Morphological Diversification under High Integration in a Hyper Diverse Mammal Clade

Abstract

Diversification and adaptive radiations are tied to evolvability, which in turn is linked to morphological integration. Tightly integrated structures typically evolve in unison, whereas loosely integrated structures evolve separately. Highly integrated structures are therefore thought to constrain evolutionary change by limiting morphological disparity. Mounting evidence suggests that high integration may facilitate evolutionary change along a single trajectory. We used geometric morphometrics to compare cranial disparity and integration among phyllostomid bats-which exhibit the greatest dietary diversity of any mammalian family-and their sister taxa within the superfamily Noctilionoidea. Our results reveal that phyllostomids are more tightly integrated and have less disparity in cranial shape than their outgroups, despite exhibiting tenfold higher species richness and significantly increased rates of speciation. Phyllostomid cranial morphology appears to have diverged from that of other noctilionoids by evolving along a single axis of morphological variation that describes the relative length of the rostrum. We propose that phyllostomids were able to evolve to occupy a wide range of dietary niches by varying rostrum length, possibly along a line of least evolutionary resistance. This study provides a compelling empirical example of how increased integration can lead to adaptation, implying that both high and low integration can underlie diverse phenotypes in adaptive radiation.

The evolutionary diversity of locomotor innovation in rodents is not linked to proximal limb morphology

“…Additional factors, such as environmental change [60][61][62] may also have led to increased taxonomic diversification in rodents. Muroids, in particular, have been hugely successful at range expansions and novel introductions to new regions in comparison with more morphologically specialized groups or those with multiple locomotor modes 14 . These results in modern rodents allude to how small, generalist early mammals may have been so successful at quickly proliferating into multiple locomotor modes following niche openings after the Cretaceous-Tertiary boundary 63,64 .…”

“…While major evolutionary radiations can often be traced back to the origin of a completely novel structure (e.g., wings in birds, bats, and pterosaurs), smaller-scale radiations have also been tied to increased morphological adaptability. For example, morphological variation in the skulls of stenodermatine bats have allowed specialization on fruit rather than insects, which in turn led to an increase in their speciation rates (e.g., [9][10][11][12][13][14]. While the linkage between morphological novelties and evolvability, taxonomic diversification, and the invasion of novel niches is often hypothesized, it is rarely tested quantitatively because this requires both repeated convergence and a well-resolved phylogeny for estimating diversification.…”

Differential cellular proliferation underlies heterochronic generation of cranial diversity in phyllostomid bats

“…2). Thus, we focus on phyllostomid species, which feature significant differences in overall cranial length [15,31] that we could collect from the wild: Carollia perspicillata, a predominantly frugivorous bat [56,78] with a face near the center of cranial shape morphospace (Fig. 2); Artibeus jamaicensis, a predominantly frugivorous bat [41] with a short and wide face; and Glossophaga soricina, a predominantly nectarivorous and pollenivorous bat [12] with an elongated head and narrow face.…”

Phenotypic integration in feliform carnivores: Covariation patterns and disparity in hypercarnivores versus generalists

“…However, relationships between integration patterns and shape diversity are now understood as more complex than previously thought. For example, high integration has been proved to also promote the evolution of coordinated traits through novel phenotypes (Goswami et al 2014Hu et al 2016;Felice et al 2018;Hedrick et al 2020). Phenotypic integration and modularity can be investigated at different levels of organization, from modules within one structure to phenotypic-genetic integration, through both exploratory and confirmatory analyses (e.g., Klingenberg 2009;Goswami and Polly 2010;Klingenberg, 2013Klingenberg, , 2014Goswami et al 2014;Goswami and Finarelli 2016).…”