Ecological Morphology of Neotropical Bat Wing Structures

Abstract

Morphology has a direct influence on animal fitness. Studies addressing the identification of patterns and variations across several guilds are fundamental in ecomorphological research. Wings are the core of ecological morphology in bats; nevertheless, individual bones and structures that support the wing, including metacarpals, phalanges and the length of digits, have rarely been the subject of comprehensive research when studying wing morphology. Here, I analyzed morphological variations of wing structures across 11 bat guilds and how individual bone structures are correlated to diet, foraging mode and habitat use. I obtained wing measurements from 1512 voucher specimens of 97 species. All the specimens analyzed came from the Mammalian Collection at the Museo Javeriano de Historia Natural of Pontificia Universidad Javeriana (MPUJ-MAMM) (Bogotá, Colombia). Positive correlations between size and the length of the third and fifth digit were detected. Bat guilds that capture their preys using aerial strategy in uncluttered habitats had longer third digits but short fifth digits compared to guilds that rely on gleaning strategy and forage in highly cluttered space. Although terminal phalanges were shown to be important structures for guild classification, metacarpals were strongly related to aerial foragers from uncluttered habitats because of their potential role in flight performance and ecological adaptations. Results show that habitat use, as well as foraging mode, are reflected in wing structures. Different wing traits to those evaluated in this study should be considered to better understand the ecological interactions, foraging strategy, wing adaptations, and flight performance in Neotropical bats.

Keywords: Chiroptera; Ecomorphological relationships; Flight pattern; Guild; Wing traits.

Fig. 1.

Wing traits measured from bat specimens. Wing structures (metacarpals and phalanges) are represented in the figure. Wing digit length is the sum of metacarpals and phalanges of each digit.

Fig. 2.

Frequency histograms of wing variables for 97 Neotropical bat species. Variables include (a) forearm length (b) length of the third digit (c) length of the fourth digit and (d) length of the fifth digit.

Fig. 3.

Principal wing variables of 97 Neotropical bat species. Variables include (a) wing length (LD3/FL ratio) and (b) wing width (LD5/FL ratio). Acronyms for bat species are defined in table 1.

Fig. 4.

Scatter plot of wing digits for the 97 Neotropical bat species. Figures include (a) correlation between LD3 and FL, exploring the correlation of hand-wing length and bat size; (b) correlation between LD5 and FL, assessing the correlation of wing width and bat size; and (c) correlation between LD3 and LD5, showing the correlation of hand-wing length and wing width. Acronyms for bat species are defined in table 1.

Fig. 5.

Boxplots of wing ratios among 11 Neotropical bat guilds. Comparisons include (a) LD3/FL ratio, (b) LD5/FL ratio, and (c) LD3/LD5 ratio. Acronyms for bat guilds are defined in table 1.

Fig. 6.

Multidimensional Scaling (MDS) ordination plot showing variation of individual bone structures among bat guilds. Each dot represents a species and the relative distance between two points reflect the relative dissimilarity. Polygons represents each one of the bat guilds. Metacarpals and phalanges are scaled to size (i.e., wing structure /FL ratio) and are found in figure 1. Acronyms for bat guilds are defined in table 1.