Environmental determinism, and not interspecific competition, drives morphological variability in Australasian warblers (Acanthizidae)

Abstract

Interspecific competition is thought to play a key role in determining the coexistence of closely related species within adaptive radiations. Competition for ecological resources can lead to different outcomes from character displacement to, ultimately, competitive exclusion. Accordingly, divergent natural selection should disfavor those species that are the most similar to their competitor in resource use, thereby increasing morphological disparity. Here, we examined ecomorphological variability within an Australo‐Papuan bird radiation, the Acanthizidae, which include both allopatric and sympatric complexes. In addition, we investigated whether morphological similarities between species are related to environmental factors at fine scale (foraging niche) and/or large scale (climate). Contrary to that predicted by the competition hypothesis, we did not find a significant correlation between the morphological similarities found between species and their degree of range overlap. Comparative modeling based on both a priori and data‐driven identification of selective regimes suggested that foraging niche is a poor predictor of morphological variability in acanthizids. By contrast, our results indicate that climatic conditions were an important factor in the formation of morphological variation. We found a significant negative correlation between species scores for PC1 (positively associated to tarsus length and tail length) and both temperature and precipitation, whereas PC2 (positively associated to bill length and wing length) correlated positively with precipitation. In addition, we found that species inhabiting the same region are closer to each other in morphospace than to species outside that region regardless of genus to which they belong or its foraging strategy. Our results indicate that the conservative body form of acanthizids is one that can work under a wide variety of environments (an all‐purpose morphology), and the observed interspecific similarity is probably driven by the common response to environment.

Biotic and abiotic drivers of evolution in some Australian thornbills (Passeriformes:Acanthiza) in allopatry, sympatry, and parapatry including a case of character displacement

“…We then use these two inter‐ and intraspecific patterns of diversity to explore the history of the species’ diversification, in particular across their putative hybrid and contact zones. Our study expands on that of García‐Navas, Rodríguez‐Rey, Marki, and Christidis (2018;) who concluded that climate is a key predictor of morphological diversity in the family Acanthizidae to which thornbills belong.…”

Niche theory and its relation to morphology and phenotype in geographic space: a case study in woodpeckers (Picidae)

“…Parallel analyses should compare pairs of taxa with similar phylogenetic and ecological relatedness that co-occur broadly and do not share similar phenotypes to provide a null comparison of sympatric ecogeographic variation in systems lacking mimicry. If results are similar to those found in mimicry systems, then communities' ecomorphological evolution as a whole are likely being driven by other abiotic and biotic factors (García-Navas et al 2018).…”

Otolith morphological divergences of successful Lessepsian fishes on the Mediterranean coastal waters

“…The morphological disparity is often used as a surrogate measure of biological diversity in the study of biological communities (Neustupa et al, 2009;Farré et al, 2013). This diversity is historically generated by ecological and evolutionary factors varying across scales of space and time producing variability among different geographical regions (Ricklefs, 2004;Witman et al, 2004;García-Navas et al, 2018). However, these morphological gaps between regions are being increasingly homogenized by human assisted translocation of species to global scale (McKinney and Lockwood, 1999), and the morpho-functional differentiation of nonindigenous species can be the key to gain a competitive advantage and develop invasive populations (Smith and Knapp, 2001;Azzurro et al, 2014;Nagelkerke et al, 2018).…”