An analysis of the relative importance of biotic and abiotic factors to the niche of the cockroach genus Arenivaga (Rehn) (Blattodea: Corydiidae)

Abstract

Arenivaga occur across the American Southwest and Mexico, as well as in the scrub and high pine communities of Florida. This study analyzes the relative contribution of 22 abiotic and one biotic variable to the niche of the genus Arenivaga. This analysis revealed that more than 95% of their ecological niche is described by eight variables: soil, isothermality, minimum temperature of the coldest month, mean temperature of the driest quarter, annual precipitation, precipitation of the driest month, precipitation of the wettest quarter and ground cover. These eight variables with respect to their relative contributions to the niche of the genus as a whole as well as the individual niches of 27 species in the genus were then examined. This revealed the similarity of niche composition of most of the species, as well as how varied the niches were of several species. A species dendrogram built from similarity of contribution of the eight variables to niche composition was compared to a phylogeny of the genus, but few similarities in topology were found. This analysis revealed that soil is the most important contributor to these species' niches, followed by precipitation of the driest month, and finally, precipitation of the wettest quarter. It also confirmed that the majority of Arenivaga species have niches comprised of similar, but not identical, proportions of as few as four, and as many as eight ecological variables. Currently there is no evidence to support niche conservatism between closely related species, indicating that adapting to new and variable niches is one of the drivers of speciation in this genus.

A biogeographical profile of the sand cockroach Arenivaga floridensis and its bearing on origin hypotheses for Florida scrub biota

“…The three lineages were again recovered (all PP = 1.0) in the concatenated BI analysis but with higher nodal support for the Atlantic‐Central/Lake Wales clade (PP = 0.98; Figure ) than in the cox2 tree (PP = 0.79). The concatenated tree also reveals strongly supported interspecific relationships (all PP = 1.0), which are topologically congruent with Hopkins and Giermakowski's () molecular–morphological phylogeny for the genus. Namely, Arenivaga floridensis is recovered as the sister taxon to an A. erratica + A. tonkawa clade, whereas the species A. gumperzae , A. gaiophanes , and A. bolianna represent increasingly divergent clades.…”

“…Otherwise, the eastern range boundary of A. bolliana terminates in Texas (some 1,400 km west); if viable populations do occur in Florida, they were probably recently introduced and remain extremely localized. Hopkins and Giermakowski's () phylogeny of Arenivaga (24 of the 48 species) identified A. erratica as the sister species to A. floridensis , providing consistency with an earlier morphological interpretation that placed A. floridensis in the “ erratica group” (Hebard, ). Our phylogeny differs slightly, recovering a sister group relationship between A. floridensis and A. erratica + A. tonkawa .…”

“…Hopkins’ () BI consensus trees for DNA sequence data, generated separately for cox1 , 12S, and H3 genes, depict slightly different relationships among these three species, although all are invariably recovered in the same clade. Topological placement of A. floridensis , relative to other congeners, reveals a derived position within the genus, both in our BI tree and in Hopkins and Giermakowski's () phylogeny. As well, their phylogeny depicts a Baja California endemic , Arenivaga diaphana Hopkins, as the sister taxon to the remaining 23 species surveyed, which corroborates southwestern North America as the center of origin for Arenivaga .…”

“…Our phylogeny differs slightly, recovering a sister group relationship between A. floridensis and A. erratica + A. tonkawa . This topological discrepancy probably reflects the influence of morphological characters in Hopkins and Giermakowski's () integrated dataset. Hopkins’ () BI consensus trees for DNA sequence data, generated separately for cox1 , 12S, and H3 genes, depict slightly different relationships among these three species, although all are invariably recovered in the same clade.…”

“…To explore aspects of origin and dispersal, we also generated cox2 sequences for five additional species of Arenivaga . One species, Arenivaga erratica Caudell, is the putative sister species to A. floridensis , whereas the remaining four, Arenivaga tonkawa Hebard, Arenivaga gumperzae Hopkins, Arenivaga gaiophanes Hopkins, and Arenivaga bolianna (Saussure), represent increasingly divergent clades within the genus (Hopkins & Giermakowski, ). We combined cox2 data for the western species and 32 A. floridensis (representing all major and minor ridges in our sample) with sequence data for two additional loci, mitochondrial cytochrome oxidase I ( cox1 ) and nuclear histone 3 ( H3 ), amplified as detailed in Table .…”