Figure 1.
Fossil calibrated Cytochrome B species tree.
The main clades are coloured as follows: Marsupial mammals (brown); Euarchontoglires (grey); Laurasiatheria (green); Yangochiroptera (yellow); echolocating Yinpterochiroptera (blue); Pteropodidae (orange). The estimated divergence times of Marsupial mammals, Euarchontoglires; Laurasiatheria and Chiroptera are shown on the corresponding nodes.
Figure 2.
X-ray projections through the posterior portion of bat skulls containing the bony labyrinth, in the ventral-dorsal plane.
The corresponding reconstructed inner ear volumes are shown on the right of the panels; these inner ears are orientated so that the lateral semicircular canals are maximally aligned in the horizontal plane, allowing differences in cochlear orientation to be compared across species. Echolocation mode, species and family information are as follows: (A) the non-echolocating Old World fruit bat Hypsignathus monstrosus (1.3518) (Pteropodidae); (B) the Old World CF bat Rhinolophus ferrumequinum (58.20697) (Rhinolophidae); (C) the New World CF bat Pteronotus parnellii (5.21236) (Mormoopidae) and (D) Mormoops megaphylla (2.1603) (Mormoopidae) which utilizes narrowband multi-harmonic signals.
Figure 3.
Log semicircular canal radius (R) versus log body mass0.33– for (A) anterior, (B) lateral and (C) posterior semicircular canals across bats [Old World fruit bats (orange); echolocating Yinpterochiroptera (blue); Yangochiroptera (yellow)] and non-flying mammals [species designated as small body-sized (black) and species designated as large body-sized (grey) according to the data].
95% prediction intervals (dashed lines) and 95% confidence intervals (solid lines) are shown for the mammal regression lines. Lateral semicircular canal size of echolocating bats showed the most variation of all three canals; species falling above the 95% PI (and thus larger lateral canals than expected) were six Rhinolophus spp., Rhinopoma hardwickii, Cardioderma cor and Pteronotus parnellii. Across all three canals, species with consistently larger canals included C. cor and Rhinolophus megaphyllus and those with consistently smaller were Cloeotis percivali, Rhinolophus philippinensis (small morph) and Macroderma gigas. However, it should be noted that OLS regression prediction and confidence intervals calculated assume independent data points and, therefore, the intervals presented here may underestimate the actual values.
Figure 4.
Relative size of the three semicircular canals within bats.
The three canals are depicted as follows: anterior – diamonds; lateral – triangles and posterior – circles. With members of the two bat clades represented as follows: Yinpterochiroptera [Old World fruit bats (orange), laryngeal echolocating species (blue)] and the Yangochiroptera (yellow). Species numbers follow those in Table S1 in Text S1.
Figure 5.
Relative (A) anterior, (B) lateral and (C) posterior semicircular canal size versus relative cochlea size.
The OLS regression of non-bat mammals is shown by the bold line (anterior: r = 0.954, P = 3.48×10−20; lateral r = 0.946, P = 1.91×10−21; posterior r = 0.951, P = 7.29×10−21), and the 95% confidence and prediction intervals are shown by the solid and dashed lines respectively. Non-bat placental mammals (grey circles) and marsupial mammals (grey triangles) from Spoor et al. [17]. Pteropodidae (orange circles), Yangochiroptera (yellow circles), Pteronotus parnellii (gold circle), Rhinolophidae (dark blue circles), and remaining echolocating Yinpterochiroptera (medium blue circles) represent the bat species included by this study.
Figure 6.
A sample of the bat families studied with ecomorphological characters mapped onto the phylogeny.
Bat phylogeny to show species representation based on Teeling et al. [34]. Family call types are taken from Jones and Teeling [41]; no laryngeal echolocation (white); short, broadband, multiharmonic (yellow); narrowband, multiharmonic (purple); constant frequency (blue); narrowband, dominated by fundamental harmonic (green). Labyrinths obtained from this study include Yangochiroptera (dark grey bar): Mormoops megalophylla (a), Pteronotus parnellii (b), Trachops cirrhosus (c), Cheiromeles torquatus (d), Lasiurus borealis (e) and Saccopteryx bilineata (f); Yinpterochiroptera (light grey bar): Rousettus aegyptiacus (g), Rhinolophus pearsonii (h), Hipposideros ridleyi (i), Rhinopoma hardwickii (j) and Lavia frons (k). Representative wing outlines, traced from published figures, as follows: Morpmoops blainvillii (i) (modified from [86]); Pteronotus parnellii portoricensis (ii) (modified from [86]); Artibeus jamaicensis jamaicensis (iii) (modified from [86]); Tadarida pumila (iv) (modified from [49]); Pipistrellus pipistrellus (v) (modified from [49]); Taphozous melanopogon (vi) (modified from [87]); Eidolon helvum (vii) (modified from [49]); Rhinolophus ferrumequinum (viii) (modified from [88]); Hipposideros abae (ix) (modified from [89]); Rhinopoma hardwickii (x) (modified from [89]); Lavia frons (xi) (modified from [49]). Plots represent family distributions along shape axes of the anterior semicircular canal eigenshape 1 (AES1) and anterior semicircular canal eigenshape 2 (AES2).