Fig 1.
Summary of mating and male morphology in leiobunine harvestmen.
(a) Precontact between male and female Leiobunum verrucosum (male left, female right), with legs removed for clarity. (b) Precopulatory position of mating pair. Male pedipalps grasp female behind coxae of second pair of legs; penis is inserted into female's mouth and then positioned at pregenital opening. (c) Ventral view of male L. verrucosum with short penis retracted and extended by hydraulic expansion of hematodocha. (d) Ventral view of male Hadrobunus fusiformis (not included in study but anatomically similar to L. hoffmani) with long penis retracted and extended by protractor muscles. Abbreviations: f, fultura; go, genital operculum; h, hematodocha; m, mouth; p, penis; pgo, pregenital opening; pp, male pedipalp; ppm, penis protractor muscle; s, nuptial gift sac.
Fig 2.
Phylogeny of leiobunines of eastern North America and examples of genitalic diversity.
(a) Maximum clade credibility tree of 28 species used in phylogenetic comparative analyses, with parsimonious distribution of character-state combinations of penile nuptial gift sacs and female pregenital barrier mapped on branches. Scale = substitutions per site. (b) Examples of penes (dorsal view) and female genital operculum (internal dorsal view), with sclerotized pregenital barrier shaded. All drawings to same scale. Genus abbreviations: E, Eumesosoma; H, Hadrobunus; L, Leiobunum; Le, Leuronychus; T, Togwoteeus. Numbers after species names are used as data-point labels in Fig 3.
Table 1.
Overview of structural traits measured, including sex investigated, transformation of carapace width (W) for dimensional size-correction based on isometric expectation, and hypothesized effect on reproductive strategy.
Fig 3.
Evidence for sexual coevolution among reproductive traits and arrangement of species along a spectrum of mechanical antagonistic potential.
(a) Species scores on canonical function 1 from phylogenetic canonical correlation analysis of eight male and two female mechanical variables. (b) Bivariate phylogenetic regression of relative closing force of the female pregenital opening, and relative protraction force of the penis. (c) Phylogenetic principal components analyses (pPCA) of all variables, including male and female body size(PCs 1 and 2: 57.52% variance, λ = 6.75e-5, lnL λ = 175), demonstrating that PC1 is not the size axis. (d) pPCA of all reproductive variables without body size. See Table 2 for PC loadings and other details of PCAs.
Table 2.
Trait loadings of phylogenetic principal component analyses with and without body size, eigenvalues, and percent variance explained by first two principal components.