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

Abstract

Florida scrub is a xeric ecosystem associated with the peninsula's sand ridges, whose intermittent Pliocene–Pleistocene isolation is considered key to scrub endemism. One scrub origin hypothesis posits endemics were sourced by the Pliocene dispersal of arid‐adapted taxa from southwestern North America; a second invokes Pleistocene migration within eastern North America. Only one study to date has explicitly tested these competing hypotheses, supporting an eastern origin for certain scrub angiosperms. For further perspective, we conducted a genetic analysis of an endemic arthropod, the Florida sand cockroach (Arenivaga floridensis), with two aims: (1) to reconstruct the peninsular colonization and residence history of A. floridensis and (2) determine whether its biogeographic profile favors either origin hypothesis. We sequenced the cox2 mitochondrial gene for 237 specimens (65 populations) as well as additional loci (cox1, nuclear H3) for a subset of Florida roaches and congeners. Using Network and Bayesian inference methods, we identified three major lineages whose genetic differentiation and phylogeographical structure correspond with late Pliocene peninsula insularization, indicating Arenivaga was present and broadly distributed in Florida at that time. Stem and crown divergence estimates (6.36 Ma; 2.78 Ma) between A. floridensis and western sister taxa span a period of extensive dispersal by western biota along an arid Gulf Coast corridor. These phylogeographical and phylogenetic results yield a biogeographic profile consistent with the western origin hypothesis. Moreover, age estimates for the roach's peninsular residence complement those of several other endemics, favoring a Pliocene (or earlier) inception of the scrub ecosystem. We argue that eastern versus western hypotheses are not mutually exclusive; rather, a composite history of colonization involving disparate biotas better explains the diverse endemism of Florida scrub.

Pleistocene diversification of unifoliolate‐leaved Lupinus (Leguminosae: Papilionoideae) in Florida

“…Similarly striking biogeographic differences in the biota of Florida sand ridges occur in other xeric endemic taxa (e.g. Branch & Hokit, 2000; Christman & Judd, 1990; Deyrup, 2005; Deyrup & Cover, 2004; Hill, 2023; Lamb et al., 2018; Schoonover McClelland et al., 2023). All this suggests a central role for sand ridge edaphic niche conservatism and allopatric non‐adaptive divergence in the differentiation of these variants, and indeed across the Florida unifoliolate species clade as a whole, as found for other Floridian sand ridge plant clades (e.g.…”

“…Similarly striking biogeographic differences in the biota of Florida sand ridges occur in other xeric endemic taxa (e.g. Branch & Hokit, 2000;Christman & Judd, 1990;Deyrup, 2005;Deyrup & Cover, 2004;Hill, 2023;Lamb et al, 2018;Schoonover McClelland et al, 2023). All this suggests a central role for sand ridge edaphic niche conservatism and allopatric F I G U R E 3 Barplots depicting genetic structure based on the nextRADseq dataset (a-c) across all Florida Lupinus specimens and (d, e) across specimens assigned to L. cumulicola clade.…”

A new species of pygmy mole cricket (Orthoptera: Tridactylidae) from the Lake Wales ridge of Florida and new records of Ellipes eisneri from the northern Brooksville ridge

“…In the right conditions, it can be quite abundant, but only those knowing what to look for are likely to come across it. The genus Ellipes is now known to contain two rather distinct upland species with restricted ranges in Florida, whereas populations of scrub Neotridactylus are more ambiguous, perhaps consisting of only one wide-ranging, variable scrub species in a similar situation to the Florida endemic cockroach Arenivaga floridensis Caudell, which is also restricted to scrub and sandhill (Lamb et al 2018). The status of scrub Neotridactylus will be explored in a forthcoming paper.…”