Nonadaptive radiation in damselflies

Abstract

Adaptive radiations have long served as living libraries to study the build‐up of species richness; however, they do not provide good models for radiations that exhibit negligible adaptive disparity. Here, we review work on damselflies to argue that nonadaptive mechanisms were predominant in the radiation of this group and have driven species divergence through sexual selection arising from male–female mating interactions. Three damselfly genera (Calopteryx,Enallagma and Ischnura) are highlighted and the extent of (i) adaptive ecological divergence in niche use and (ii) nonadaptive differentiation in characters associated with reproduction (e.g. sexual morphology and behaviours) was evaluated. We demonstrate that species diversification in the genus Calopteryx is caused by nonadaptive divergence in coloration and behaviour affecting premating isolation, and structural differentiation in reproductive morphology affecting postmating isolation. Similarly, the vast majority of diversification events in the sister genera Enallagma and Ischnura are entirely driven by differentiation in genital structures used in species recognition. The finding that closely related species can show negligible ecological differences yet are completely reproductively isolated suggests that the evolution of reproductive isolation can be uncoupled from niche‐based divergent natural selection, challenging traditional niche models of species coexistence.

Range shifting species reduce phylogenetic diversity in high latitude communities via competition

“…). The maintenance of a similar niche across a broad phylogenetic scale within damselflies is consistent with earlier studies showing that speciation in damselflies is rarely linked to niche divergence (McPeek, Brown & Apr ; Wellenreuther & Sánchez‐Guillén ). Our results extend these previous findings by demonstrating that, like speciation, competitive displacements in damselflies is also unrelated to levels of niche divergence.…”

Phenotypic disparity in Iberian short-horned grasshoppers (Acrididae): the role of ecology and phylogeny

“…This model of radiation exemplifies that episodes of ecological opportunity can be recurring over the evolutionary history of a lineage [24]. Beyond the epithet “adaptive”, non-adaptive radiations (or morphostatic radiations) constitute another form of radiation that remains largely unstudied [25–27]. Non-adaptive radiations arise through processes that are unrelated to niche exploitation and the resulting species usually exhibit low morphological disparity and allopatric distributions [28].…”

Transcriptome profiling in the damselfly Ischnura elegans identifies genes with sex-biased expression

“…We conduct novel gene expression analyses in adult male and female Ischnura elegans damselflies (family Coenagrionidae) to investigate sex differences in gene expression in general, and to identify transcripts of genes associated with pathways of potential importance for sexual development and sexual conflict in particular. Ischnura elegans is an evolutionary and ecological model species because of its ancient taxonomic position [14], the presence of a genetically controlled female-limited colour polymorphism [15, 16], and strong sexual conflict (reviewed in [17]). It is also an emerging odonate genetic model species, with the most complete male-specific annotated transcriptome of any odonate to date [18], a solid understanding of the inheritance of colour [16], a linkage map [19] and ongoing work to assemble the genome (Wellenreuther et al in preparation).…”