https://orcid.org/0000-0003-3056-4897
Figures
Abstract
Geopsammodius Gordon and Pittino, 1992 are sand-dwelling beetles found throughout the southeastern United States, Texas, and Honduras. Their modified morphology including reduced flight wings, reduced eyes, expanded tibiae, and fused elytra suggests their evolutionary history may be closely tied to the sand dunes in which they inhabit. Here, using six genes, we reconstruct the relationships of species within the genus and members of the tribe Psammodiini. We then performed divergence time estimation in order to determine the age of the group. We recovered Parapsammodius Verdú, Stebnicka, and Galante, 2006 outside the Psammodiini indicating the need for future taxonomic revision. Within the genus Geopsammodius, we found two major clades that largely correspond with geography. The first occurring along the east coast and Gulf Coast and the second clade occurring inland in Florida and Georgia. We find that the age of Geopsammodius coincides with the formation of extensive sand dunes (20–23 MYA) suggesting that the group may have evolved concurrently with this sandy habitat.
Citation: Schnepp KE, Saxton NA, Powell GS, Gunter NL, Skelley PE, Cave RD (2026) Phylogeography of Geopsammodius Gordon and Pittino, 1992 (Coleoptera: Scarabaeidae: Aphodiinae): A radiation of endemic psammophilic beetles. PLoS One 21(8): e0351948. https://doi.org/10.1371/journal.pone.0351948
Editor: Muhammad Asghar Hassan, Sun Yat-sen University - Shenzhen Campus, CHINA
Received: March 3, 2026; Accepted: June 3, 2026; Published: August 12, 2026
Copyright: © 2026 Schnepp et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All sequences are available via NCBI (https://www.ncbi.nlm.nih.gov/genbank/) and the relevant accession numbers have been uploaded as Supporting Information.
Funding: The author(s) received no specific funding for this work.
Competing interests: The authors have declared that no competing interests exist.
Introduction
A number of traditionally surface-dwelling terrestrial lineages have shifted to underground habitats, be it to shelter from weather or predators, to find food, or to nest in. Throughout the animal kingdom, subterranean animals with special modifications to live underground include some amphibians, fishes, insects, lizards, mammals, marsupials, millipedes, and spiders [1–6]. These modifications can include enlarged and shortened legs, long and thin elongated legs, addition or loss of hair or setae, reduction or loss of vision, and loss of pigment [7]. The combination of subterranean habitats and the often limited dispersal abilities of these animals allow for the investigation of unique selective pressures on the evolutionary history of these taxa [8]. The field of subterranean biology includes many different microhabitat types, including caves, rock fissures, scree slopes, alluvial and colluvial material, and seepage springs, as well as the microclimates that subterranean habitats experience [9–16]. While subterranean habitats such as larger caves allow for humans to physically enter and search for insects, this habitat also often requires specialized collecting techniques to properly survey. This field of study is growing, and many recent publications discuss habitat types and the specialized methods needed to study these inaccessible environments [17–22].
Subterranean animals have disparate levels of adaptation and requirements for living underground. The ability to fly is one of the major evolutionary adaptations that allowed insects to become the dominant and most diverse form of life on earth. The loss of flight is significant as it limits dispersal and finding mates, food, shelter, and proper substrate for laying eggs [23]. In spite of the many costs of going flightless or moving underground, occupying subterranean microhabitats might represent an adaptive zone for many lineages as there are underutilized resources, less competition, and protection from predators. Subterranean species are often associated with homogeneous environments, such as deserts, islands, and caves, and can sometimes reach rather large population sizes in their specific niche [24].
There are many examples of insects moving underground and developing adaptations for subterranean life, including species of Blattodea, Coleoptera, Diptera, Hemiptera, Hymenoptera, Orthoptera, and Zygentoma [25–32]. Among the major groups of insects, Coleoptera, or beetles, make up a significant portion of the subterranean fauna.
Within beetles, several families, including Coccinellidae, Dryopidae, Dytiscidae, Elmidae, Histeridae, Hydrophilidae, Noteridae, Tenebrionidae, and Zopheridae, have at least a few members specializing in underground habitats [33–41]. Lineages in Salpingidae [42] and Dermestidae [43] have also specialized to live in anthropogenic situations to such a degree that they are essentially subterranean. Other families (i.e., Carabidae, Curculionidae, Leiodidae, and Staphylinidae) have a large number of disparately related species that occur in subterranean habitats and have significant adaptations for this specialized environment [44–52].
The scarab subfamily Aphodiinae is composed of 12 generally accepted tribes, 386 genera, and approximately 3,600 species and occurs worldwide [53]. Future effort to expand the available molecular data and increase the taxon sampling will likely elucidate more accurate relationships between subfamilies, tribes, and genera. One common name for the Aphodiinae is “small dung beetles” or “aphodiine dung beetle”, distinguishing them from the Scarabaeinae, or “dung beetles”. While these common names may be accurate in that many genera and species are obligately associated with various animal dung, there are many large lineages that appear to have no association with dung at all, occupying decaying detritus, tree holes, and various nests [54,55]. Even within the dung feeding clades, there are many atypical behaviors and niche preferences that show extreme specialization. One niche that is commonly colonized is in association with accumulations of sand, where the beetles likely consume tiny pieces of organic matter [55]. Many tribes have a large number of taxa that are specialized and isolated to different sandy microhabitats, called psammophiles [55]. Some of these psammophiles occur in massive dunes systems that span hundreds of square kilometers, while others are associated with alluvial or colluvial systems that are made of silt, clay, or gravel but also contain a portion of sand (Figs 1A–C) [56,57]. One tribe of Aphodiinae, the Psammodiini, are almost exclusively associated with sandy habitats [55].
(A) Archbold Biological Station, Lake Placid, Florida. (B) Scrub habitat near Naples, Florida. (C) Ohoopee Dunes near Reidsville, Georgia. (D) Geopsammodius hydropicus (Horn).
Placement of genera into Psammodiini is generally done with the following suite of characters: head distinctly granulate; pronotum with up to five transverse furrows separated by swellings; longitudinal furrow often present on the pronotum; elytra with a basal bead; pygidium with a long basal groove; and metatarsomeres often triangularly expanded, especially the basal tarsomere [56]. Additional diagnostic features include the type of male genitalia and details of the epipharyngeal and maxillary structures of the mouthparts [58]. The tribe Psammodiini contains approximately 26 genera and 400 species worldwide, with 15 genera and 89 species occurring in the New World [59,60]. When looking at the Psammodiini in relation to other Aphodiinae, especially Eupariini, problems with the classification arise. While the diagnostic characters given above are useful, they are not explicitly synapomorphies. Cartwright [61] discusses the similarities between Psammodius Fallén, 1807, currently split into several different genera, and Ataenius Harold, 1867 and suggests that members of both genera should probably be placed in the same tribe within Aphodiinae. Most, if not all, Psammodiini are associated with sand or sandy soils [55], and it is expected that the morphology of members in this niche would reflect this. Many of the diagnostic characters for the tribe may simply be homoplasious, convergent within specific clades of Aphodiinae, due to their similar lifestyle.
Within the Psammodiini, the genus Geopsammodius Gordon and Pittino, 1992 was proposed for two species previously in Psammodius, Psammodius hydropicus Horn, 1877 (the type species for the new genus) and Psammodius relictillus Deyrup and Woodruff, 1991 [59]. A third species was described by Lavalette [62], and an additional eight species were described by Skelley [57], who provided natural history notes and a key to species and proposed species-groups based on morphological characters. These groups consist of the relictillus species-group with five species, the hydropicus species-group with two species, and the rileyi species-group with two species. Geopsammodius atlantida Skelley, 2006 and Geopsammodius sabinae Lavalette, 1999 were ungrouped. He also made note of difficulties in understanding the distribution and species delimitation of Geopsammodius rileyi Skelley, 2006 and Geopsammodius unsidensis Skelley, 2006 in the coastal and inland sand dunes of Texas.
Species of Geopsammodius differ from those in the genus Psammodius and most of the Psammodiini in having significantly reduced eyes and flight wings (Figs 1D, 2A). With reduced eyes and reduced dispersal capabilities, populations are inclined to become isolated, and there is significant potential for speciation events. As is presently understood, species in the genus inhabit current and ancient sand dunes in the southeastern United States (Fig 3) and Honduras, where they are found in loose, soft sand. Dunes began to form in peninsular Florida approximately 23 MYA [63] as sand was moved to the region and deposited, and they have been growing at various times since, depending on sea level. These active and relictual dunes contain many isolated and endemic species that occur nowhere else [64–69]. A proposed sister genus, Leiopsammodius Rakovic, 1981, has similar natural history and morphological characters but has fully functional eyes and wings. Due to the lack of additional characters, it is unclear whether reduced eyes and wings are a synapomorphy shared by a monophyletic Geopsammodius or if this character state belongs to a lineage nested in the middle of Leiopsammodius. Here, we test the monophyly of Geopsammodius and the Psammodiini and, using fossil calibration and divergence time estimation, compare the clade age of Geopsammodius with relevant geologic events of the region.
(A) Geopsammodius relictillus (Deyrup and Woodruff). (B) Leiopsammodius deyrupi Harpootlian, Gordon, and Woodruff. (C) Neopsammodius quinqueplicatus (Horn). (D) Platytomus longulus (Cartwright).
Materials and methods
Taxon sampling
Taxon sampling included both freshly collected field samples and existing museum specimens to cover all extant described species in the region. Fieldwork was completed in the United States on public land and other localities not requiring permits, in accordance with local regulations. In total, 15 specimens representing nine of the 11 Geopsammodius species were included in the phylogenetic analyses, including all Nearctic taxa (S1 Table). Identifications were completed using Skelley [57]. All vouchers are deposited in the Florida State Collection of Arthropods (FSCA), Gainesville, FL, USA, with the exception of Ataenius alternatus (Melsheimer, 1844) that is deposited in the Queensland Museum, AUS. Nine specimens from recent sampling done by the first author were used as outgroups, comprising seven genera. Maps were generated using SimpleMappr (simplemappr.net) from historical data points [57] and specimens from the FSCA.
Molecular data
DNA extractions were completed using Qaigen’s DNeasy blood and tissue kit (Qiagen, CA, USA). Due to their small body size, non-destructive DNA extractions were performed on whole specimens by soaking the entire specimen in lysis buffer for 24 hours. The rest of the standard manufacturer protocol was followed except for the last elution step which was repeated twice with only half the suggested volume used each time. All genes, except for those associated with A. alternatus, were completed using polymerase chain reactions (PCR) with the primers and conditions listed in Tables 1 and 2. Six genes were targeted including three nuclear, 18S (~780 bps), 28S (~490 bps), and ITS2 (~440 bps), and three mitochondrial, 16S (~485 bps), COI (~640 bps), and COII (~750 bps). These sequences are available via GenBank and genus, species, locality, and unique identifiers can be found in S1 Table. Successful PCR products were sequenced at FDACS-DPI Molecular Diagnostics Laboratory, Gainesville, FL, USA, DNA Sequencing Center.
Genes for A. alternatus were extracted from Ultraconserved Element data that was generated using the Scarab_3kv1 probe set [70]. Reads were cleaned using Illumiprocessor [71], and were assembled using SPADES [72]. Target genes (see paragraph above) were searched for and extracted by using the “Map to reference” function in Geneious (Biomatters, https://www.geneious.com) with Ataenius spp. (Genbank accessions: GU226586, EU156751, EF487637) [73–75] and Aphodius sp. (MW412426) [76] used as the reference. Resulting sequences for both PCR and UCE generated data were examined for quality, trimmed, and aligned in Geneious v2022.2.2 [77] using MAFFT v.7 [78] before being concatenated for subsequent analyses (total aligned length, 3,836bps).
Phylogenetic reconstruction
Tree reconstruction was performed under maximum likelihood using IQ-TREE 2 [79] and ModelFinder [80]. Due to the rapidly evolving nature of the non-coding region ITS2 as compared to coding genes, trees both with and without the region were run. The resulting topology with ITS2 was used as a fixed topology to estimate divergence times in subsequent analyses. To use this topology, the relative ages (or heights) of nodes that were going to be constrained based on fossil evidence were adjusted by using the function chronopl applied in the R program Ape [81] so that their relative ages fell within the prior distributions of our constraints.
Divergence time estimation and lineage through time plot
BEAUti was used to prepare an xml file for subsequent analysis in BEAST v.2.7.6 [82]. The site model was set based on the results of ModelFinder (i.e., GTR + F + I + G4). We used a partitioned clock model such that a strict mitochondrial clock rate was applied to all mitochondrial genes (i.e., 0.0115) by using the standard rate found in insects [83]. The use of this mitochondrial clock was employed in conjunction with a fossil prior to estimate divergence times. We placed an exponential fossil prior (hard minimum 35 MYA, soft maximum 67.5 MYA) on the node for the MRCA of Ataenius based on the fossil Ataenius damzeni Bukejs and Alekseev, 2018 from Baltic amber. The soft maximum was based on the oldest estimated age of Eocene aphodiine fossils [84], with the 95% quantile placed at 56 MYA. Two older Cretaceous fossils were not included due to the difficulty of placing ambiguous compression fossils. Divergence time estimation was completed in BEAST. We ran multiple combinations of tree (i.e., Birth-Death and Yule) and clock models on nuclear genes (Relaxed Clock Log Normal and Relaxed Clock Exponential) with a chain length of 10 or 30 million. Results were analyzed in Tracer v.1.7.2 to ensure convergence. A consensus tree was generated for each tree and clock model combination with a 10% burn-in using TreeAnnotator. Final topologies were visualized in FigTree v.1.4.4 [85] and Adobe Illustrator v.29.0.1. The tree used for the final dated phylogeny included ITS2. A lineage through time plot was generated from the results of our divergence time estimation (Yule, Relaxed Clock Exponential) by using the “ltt.plot” function in phytools [86].
Results
Topology
The tribe Psammodiini was recovered as non-monophyletic with respect to the included Eupariini outgroups. Parapsammodius Verdú, Stebnicka, and Galante, 2006, traditionally treated in the Psammodiini, was found within a clade including the diverse genus Ataenius sister to the remaining Psammodiini. The two species of Leiopsammodius (Fig 2B) were recovered sister to Platytomus Mulsant, 1842 (Fig 2D). The clade Leiopsammodius+Platytomus was recovered as a sister group to the remaining clade of Neopsammodius Rakovic, 1986 plus a monophyletic Geopsammodius. The species of Geopsammodius formed two major groups with high support. Within these two major groups, four clades were recovered with variable support. Three of these clades loosely agree with previously described informal species-groups [57], but some notable differences warrant further investigation.
Due to the nature of noise within a non-coding region such as ITS2 at higher levels, analyses were run with (S1 Fig) and without (S2 Fig) this region included. In both phylogenetic analyses, the topology was mostly stable, and most relationships maintained high support. However, two problematic taxa with low support were present. Geopsammodius morrisi Skelley, 2006 and Geopsammodius ohoopee Skelley, 2006 consistently had low support (i.e., < 50% BS) in their placement in all trees. Additionally, G. ohoopee changed position between the two major clades recovered in this analysis.
Clade ages
Divergence time estimation (Fig 4) recovered similar clade ages across all tree and clock models, with the Birth-Death model recovering slightly older ages (Table 3). The clade age for Psammodiini+Eupariini was recovered as 69–82 MYA [51–107 HPD]. With the exclusion of Parapsammodius, a monophyletic Psammodiini was recovered with a clade age of 63–75 MYA. The recovered age for Geopsammodius is estimated to be 19–24 MYA [13–32 HPD], with most extant species appearing 7–11 MYA (Fig 4). The age recovered for the related genus Leiopsammodius is around 43–47 MYA. The lineage through time plot recovered a value of 0.033 for the slope of the line representing the average accumulation of lineages over time. Visual inspection of the time plot shows a sharp increase in lineage accumulation after 20 MYA, corresponding to the estimated age of the Geopsommadius clade as well as the proposed timing of sand dune formations in Florida (20–23 MYA [63]).
Bootstrap values <95% are shown at nodes. Vertical red bar indicates the estimated age for the early formation of most sand dunes in the southeastern United States. Lineage through time plot shows a steep increase in the number of lineages immediately following early sand dune formation.
Discussion
Systematics
From the phylogenetic results, it appears that Geopsammodius is monophyletic, having evolved from a common ancestor likely similar to Neopsammodius. Neopsammodius (Fig 2C) is a genus that is widespread in North and Central America, and its species have normally developed eyes and functional flight wings. The current distribution of Geopsammodius (Fig 3) is largely restricted to the Gulf Coast, and its species have reduced eyes and vestigial flight wings.
It appears that Parapsammodius is more closely related to Ataenius and may belong in the Eupariini, if the Eupariini are separate from the Psammodiini. Characters used to include Parapsammodius in Psammodiini are the coarsely granulate head, dentate clypeus, and vertex lacking swellings, but these characters may not always be informative in the Aphodiinae. In the description and diagnosis for Parapsammodius [58], the authors state that, while some external characters lean toward Psammodiini, the mouthparts are of the Eupariini type. Examination of additional taxa are required to understand whether or not Psammodiini and Eupariini are largely monophyletic, if the tribes contain individual lineages that need to be reclassified, or if the two tribes need to be combined.
Here, we used the fossil Ataenius damzeni for divergence time estimation. A second fossil, Ataenius europaeus Quiel, 1910 [87] also found in Baltic amber, has also been described. The description of A. europaeus certainly indicates it belongs in the Aphodiinae and most likely Eupariini, but comparison of the species with the current concept of Ataenius is impossible. Bukejs & Alekseev [88] supported the placement of A. europaeus in Ataenius, with 13 morphological characters. This example highlights the problematic nature of the genus as it is currently defined. While many of these characters allow for exclusion of a defined genus or tribe, no character or suite of characters define present-day Ataenius. Many species previously placed in Ataenius have been moved based on specific, unique characters, thus leaving Ataenius as a dumping ground for potentially disparately related species. Additional analyses with much higher taxon sampling than has been done to date is necessary to create a well-supported phylogeny to test the monophyly of not only Ataenius but also Eupariini and Psammodiini.
We were able to include nine of the eleven species from the genus Geopsammodius in our analyses. One species that was not able to be included was G. sabinae Lavalette, 1999 from French Guiana. Before specimens were available, Skelley [57] remarked on possible similarities of this species to G. atlantida Skelley, 2006. After seeing specimens, however, it is clear that G. sabinae does not belong in Geopsammodius and is most likely a member of Odontopsammodius Gordon and Pittino, 1992 without clypeal teeth. The inclusion of G. atlantida Skelley, 2006 in this study was not possible due to lack of fresh material. Additional populations or species of Geopsammodius are likely to occur between the known populations of southern Texas and the one in Honduras. It is also possible that more species or populations occur farther south in Central America or even in the West Indies. In addition to Geopsammodius, there are many additional subterranean beetles, in sandy soils in Florida, that have been described [89–93], but much additional work in this niche is necessary to clarify relationships and understand the true diversity of the region.
Additional surveying is needed in North and Central America, as specimens are rarely collected without employing specialized collecting methods. Material from many of the Texas populations would allow for additional study of the populations and determine if current species concepts and distributions are accurate. It would also elucidate whether additional species exist or one widespread variable species occurs in Texas as well as how G. atlantida is related to the rest of Geopsammodius. Similarly, additional material would allow for a study of the relictillus-group in Florida and whether clades seen in the current phylogeny represent speciation or they are simply an artifact of the distribution in the taxon sampling. Fresh specimens of untested populations of Geopsammodius and genera (i.e., Odontopsammodius, Psammodius, Rhyssemus) are necessary to get an accurate understanding of the tribe and how Psammodiini and Eupariini are related. A thorough evaluation of distributions and relationships cannot be inferred without additional specimens.
Biogeography
While the current phylogeny maintained high support throughout most of the tree, additional genes could clarify certain relationships as well as more definitely place G. morrisi and G. ohoopee, both of which had lower nodal support in our phylogenies. This would allow for a more accurate interpretation of the evolutionary history of Geopsammodius and provide insight into additional geologic events that may have influenced ancient speciation events.
At present, the two major clades in Geopsammodius appear to broadly follow a geologic origin. One clade, hydropicus+rileyi+subpedalis+unsidensis+withlacoochee, occurs along the east coast and Gulf Coast. The second clade, fuscus+morrisi+ohoopee+relictillus, occurs inland in Florida and Georgia. Within these groups, G. hydropicus (current east coast) is sister to G. subpedalis Skelley, 2006 (current Florida panhandle coast), and hydropicus+subpedalis is sister to G. withlacoochee Skelley, 2006. This relationship would indicate that, at some point, G. withlacoochee may have been separated during a glacial maximum allowing hydropicus+subpedalis to maintain itself until it, too, was separated during a recent glacial retreat. The Texas rileyi+unsidensis lineage is sister to the coastal Florida clade, indicating that at some point an ancestor of the coastal Florida clade may have dispersed past the Mississippi River, likely moving with barrier sand islands. After this potential dispersal event, the lineage split into G. rileyi Skelley, 2006 and G. unsidensis Skelley, 2006, one mainly coastal and one mainly inland. This hypothesis is complicated, however, by remaining confusion over distribution and species limits. The position of G. ohoopee is also problematic in trees with and without ITS2. There is low support for its placement in both trees, and the species changed position between the two major clades in each tree. Geopsammodius ohoopee is also unusual in that it appears to be restricted to riverine and wind deposited sand dunes in Georgia, unlike the remaining species that are associated with marine deposits.
The second inland clade, without G. ohoopee, is divided into two clades, one of these being composed of “relictillus”, or near, and the other comprising “fuscus+morrisi”. The Geopsammodius relictillus (Deyrup and Woodruff, 1991) portion of the tree indicates significant divergence and potentially new species as the two representatives from the Lake Wales Ridge are distinct from specimens collected in areas west of the ridge. Additional specimens and study of material might answer how different these populations may be. The placement of G. morrisi is also problematic as it has low support in both trees. The distribution of G. morrisi is also unusual in that it occurs in an area just east of, and is not distinctly differentiated from, the Lake Wales Ridge. Despite lower support, the phylogeny indicates that G. morrisi is sister to the two G. fuscus populations included in the study. Geopsammodius fuscus has been collected near the coast, but in sand deposits distinctly separate from the current dune system and intracoastal waterways. This would suggest that a population east of the Lake Wales Ridge, separate from G. relictillus, was established and speciated as sea levels rose and fell.
Geologic events that may have created new habitats and niches for animals in the southeastern USA are significant in number. A series of events, specifically in relation to the dated phylogeny, appear especially relevant. For most of the Cretaceous period (~100 MYA) through the Eocene (34 MYA), the Gulf Trough (Suwannee Straight) was a connection between the Gulf of Mexico and Atlantic Ocean. This trough and the current running from southwest to northeast, as well as higher sea levels during this period, allowed for a continued separation of the continental alluvial deposits and the carbonate deposits of the shallow sea covering modern day Florida [63,94,95]. In the late Oligocene and early Miocene (23 MYA), sea levels dropped, and the Appalachian Mountains experienced uplift, which in turn increased erosion rates. This decrease in sea level and increase in erosion filled the Gulf Trough and connected what had been two different depositional environments in the panhandle and peninsular Florida. This connection allowed for massive amounts of siliciclastic deposits to be moved south through longshore currents, covering much of the carbonate platform that had formed over the prior 100 million years.
Once present over Florida, these sand deposits were moved and shaped through hundreds or thousands of cycles of sea level rise and fall, shifting between 100 feet higher than today to 400 feet lower. These cycles created, destroyed, and moved islands and dune systems, thus creating many opportunities for speciation events, especially for animals with poor dispersal abilities [96]. The development of this new habitat and niche 20–23 MYA corresponds to the origin of Geopsammodius 19–24 MYA. The crown age of Geopsammodius coinciding with the beginning of the sand dune formation in Florida, and the subsequent speciation and radiation of this genus aligning with the continued deposition of sand across this region, suggests the coevolution of Geopsammodius with this sandy habitat. Once specialized for a subterranean niche by losing flight wings and having extremely reduced eyes, this lineage would have lower dispersal capabilities. Individuals would generally be subject to moving with sand, although it is possible that gene flow could occur with some specimens being blown, washed, or rafted to suitable habitat.
While testing this very close association between the origin of these beetles and the time of sand dune formation sheds light on the evolutionary history of this group, it is also likely an association shared by additional taxa of the region. Sand dunes, specifically in peninsular Florida, are home to a variety of endemic plant species, including Avon Park rattlebox (Crotalaria avonensis K.R. DeLaney and Wunderlin, 1989), scrub balm (Dicerandra frutescens Shinners 1962), scrub eryngo (Eryngium cuneifolium Small, 1933), scrub spurge (Euphorbia rosescens E.L. Bridges and Orzell, 2002), and Florida ziziphus (Pseudoziziphus celata (Judd and D.W. Hall, 1984) Hauenschild, 2016) [64,69]. Several endemic animals that are only found in these dunes include the Florida scrub jay (Aphelocoma coerulescens (Bosc 1795)), the Florida sand skink (Plestiodon reynoldsi (Stejneger, 1910)), and the Florida scrub lizard (Sceloporus woodi Stejneger, 1918) [97,98]. In addition to these animals, there are many Coleoptera restricted to the loose, deep sands of the Lake Wales Ridge of central Florida, such as Anomala eximia Potts, 1976, Cicindelidia highlandensis (Choate, 1984), Enaphalodes archboldi Lingafelter and Chemsak, 2002, Mycterus marmoratus Pollock, 1993, Odontotaenius floridanus Schuster, 1944, Onychomira floridensis Campbell, 1984, Phyllophaga okeechobea Robinson, 1948, Phyllophaga panorpa Sanderson, 1950, Pleotomodes needhami Green, 1948, Plesioclytus relictus Giesbert, 1993, Romulus globosus Knull, 1948, Selonodon archboldi Galley, 1999 and Serica frosti Dawson, 1967 [65–68,99,100]. These beetle species are relatively recently described, with the year of description averaging to 1976, very late compared to most other eastern North American species. This implies how rarely collected most of these species are and indicates that most of them inhabit very restricted and isolated niches. Such specific associations with a unique microhabitat like sand dunes leads to increased vulnerability these taxa face related to the conservation of those habitats. It is well documented that sand dune systems, especially those in Florida, are facing several risks (i.e., land use, natural disasters, sea level rise) [101,102]. Consequently, those risks are shared by the closely associated taxa that inhabit the dune systems. Studies like the present one help identify those associations and the taxa most at risk.
Supporting information
S1 Fig. Maximum likelihood cladogram showing bootstrap support including all six genes used in this study.
https://doi.org/10.1371/journal.pone.0351948.s001
(TIF)
S2 Fig. Maximum likelihood cladogram showing bootstrap support with five of the six genes used in this study, excluding ITS2.
https://doi.org/10.1371/journal.pone.0351948.s002
(TIF)
S1 Table. Taxon sampling of Scarabaeidae by genus and species, including collection locality and specimen voucher number.
https://doi.org/10.1371/journal.pone.0351948.s003
(XLSX)
Acknowledgments
For assistance in molecular sequencing we thank the Molecular Diagnostics Laboratory, Gainesville, FL, USA, Matthew Moore, and Cheryl Roberts. We thank Mayumi Needham for assistance with figures and Brandon Woo for additional fresh specimens. We thank Akito Kawahara, Jiri Hulcr, and Rebecca Kimball for their insights and guidance with this project. We also thank the Florida Department of Agriculture and Consumer Services, Division of Plant Industry, for support of this work.
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