Phylogeography and population genomics of a lotic water beetle across a complex tropical landscape

Abstract

The habitat template concept applied to a freshwater system indicates that lotic species, or those which occupy permanent habitats along stream courses, are less dispersive than lentic species, or those that occur in more ephemeral aquatic habitats. Thus, populations of lotic species will be more structured than those of lentic species. Stream courses include both flowing water and small, stagnant microhabitats that can provide refuge when streams are low. Many species occur in these microhabitats but remain poorly studied. Here, we present population genetic data for one such species, the tropical diving beetle Exocelina manokwariensis (Dytiscidae), sampled from six localities along a ~300 km transect across the Birds Head Peninsula of New Guinea. Molecular data from both mitochondrial (CO1 sequences) and nuclear (ddRAD loci) regions document fine-scale population structure across populations that are ~45 km apart. Our results are concordant with previous phylogenetic and macroecological studies that applied the habitat template concept to aquatic systems. This study also illustrates that these diverse but mostly overlooked microhabitats are promising study systems in freshwater ecology and evolutionary biology. With the advent of next-generation sequencing, fine-scale population genomic studies are feasible for small nonmodel organisms to help illuminate the effect of habitat stability on species' natural history, population structure and geographic distribution.

Biogeography and Ecological Diversification of a Mayfly Clade in New Guinea

“…The pattern found here is indeed comparable to findings by Economo et al (2015) and Jønsson et al (2014), who showed that Pheidole ant lineages and Pachycephala passerine birds, respectively, have expanded their ranges across biogeographic regions, followed by ecological filtering and a cascade pattern of dispersal from higher to lower diversity areas during these range expansions. Although ecological opportunity and taxon cycle hypotheses seem plausible explanation for the observed pattern of recent diversification associated with altitudinal shifts, we cannot exclude that it reflects the results of neutral (non-adaptive) processes (Czekanski-Moir and Rundell, 2019): spatial isolation following dispersal can also drive divergence, especially in species with low dispersal ability such as mayflies (Rutschmann et al, 2014) and in strongly structured habitat as New Guinean mountains (Janda et al, 2016;Lam et al, 2018).…”

A subterranean species of Exocelina diving beetle from the Malay Peninsula filling a 4,000 km distribution gap between Melanesia and southern China

“…This is the likely ancestral habitat type in Exocelina, with four subsequent shifts to lentic habitats (and only a few species in the lentic clades) (Toussaint et al 2015). Most species have limited geographic ranges; in one widespread epigean species population genomic studies revealed strong geographic structure even in populations as close to each other as 40 km straight line (Lam et al 2018). The lotic beetles often hide in the gravel when disturbed, and observations of M. Balke in New Guinea suggest that the interstitial of riverbanks is often utilized by these beetles, possibly to avoid downstream drift.…”

Two new species of Liodessus Guignot, 1939 diving beetles from Northern Peru (Coleoptera, Dytiscidae, Hydroporinae)

“…We use the standard genetic marker for molecular biodiversity assessment, the 5' end of the mitochondrial cytochrome c oxidase 1 gene (cox1 or CO1), also referred to as the "DNA barcode" (Hebert et al 2003) (also see the comprehensive background data in the BOLD Handbook under boldsystems.org for technical details). We are aware that this is only a single marker which is not related to speciation (Kwong et al 2012), with known issues for species delineation, including in Dytiscidae (Hawlitschek et al 2012;Hendrich et al 2010), but have found the approach very useful in many lineages at the species and even population level (Hendrich et al 2010;Lam et al 2018;Megna et al 2019). Careful cross checking of morphological and molecular taxonomic evidence is the foundation of our investigation.…”