Phylogenetics and phylogeography of a long-legged harvestman (Arachnida : Opiliones) in the Brazilian Atlantic Rain Forest reveals poor dispersal, low diversity and extensive mitochondrial introgression

Abstract

We used DNA sequence data to test the morphology-based taxonomy and examine the biogeography of the Brazilian Atlantic Rain Forest genus Promitobates. Most species are well differentiated morphologically, and a previous morphological phylogeny recovered the genus as monophyletic. However, some of these species have overlapping geographical distributions and considerable intraspecific variation, perhaps representing a species complex. Mitochondrial (12S rRNA and COI) and nuclear (ITS2 and 28S) genes were sequenced from 132 specimens collected from 27 localities. The results are consistent with significant mitochondrial introgression among the species P. ornatus, P. hatschbachi, P. lager, P. bellus and P. intermedius (the 'P. ornatus species complex'), with one specimen identified as a hybrid between P. nigripes and this complex. A phylogeographic study of the complex was conducted using mitochondrial haplotypes. This revealed remarkably poor dispersal among populations, with only one case of a shared haplotype, and very low genetic diversity. The phylogeny showed a clear break between populations on either side of a narrow region of forest, suggesting an important historical event separated these lineages in the genus. The analyses also pointed to population breaks that date back several millions of years or extremely small effective population sizes, depending on the mutation rate.

Historical signatures in the alpha and beta diversity patterns of Atlantic Forest harvestman communities (Arachnida: Opiliones)

“…It is important to mention that refugia probably did not play a role in increasing richness by promoting speciation, as Atlantic Rain Forest harvestman species appear to be much older than Pleistocene refugia (Bragagnolo et al 2015). Still, due to the optimal environmental conditions, communities from refugia may experience lower extinction rates than communities located in more unstable areas.…”

“…The large variation in altitudinal range observed in the South and Southeast may be indirectly linked to the large number of species found in these regions. A complex topography indicates a complex geomorphological history, and the emergence of mountain chains, river valleys and other geological features probably promoted the speciation of local groups and led to an increase in the regional species pool (Thomé et al 2014;Bragagnolo et al 2015;DaSilva et al 2015). DaSilva et al 2016 In contrast, the thin strip of forest in the Northeast Atlantic Rain Forest has a less complex topography, indicating that their biota had not been subjected to the vicariance events faced by the South and Southeast harvestman fauna.…”

Spatial variation in phylogenetic diversity of communities of Atlantic Forest harvestmen (Opiliones, Arachnida)

“…The basic aspects of their biology are known, for instance their nocturnal and cryptic habits, and their dependence on humidity (Pinto‐da‐Rocha et al ., ). Most tropical harvestman species have very poor dispersal capability (Mestre & Pinto‐da‐Rocha, ; Bragagnolo et al ., ), which results in a high degree of endemism (97.5% of the AF's harvestman are endemic; Pinto‐da‐Rocha et al ., ). The latter can be very informative in biogeographic studies, since the distribution of species that are poor dispersers carries a strong historical signal (Graham et al ., ; Cavender‐Bares et al ., ).…”

“…Most importantly, the taxonomy of AF harvestmen is reasonably well resolved, and several recent revisions and phylogenetic analyses are available (e.g. DaSilva & Gnaspini, 2009;Yamaguti & Pinto-da-Rocha, 2009;Bragagnolo & Pinto-da-Rocha, 2012;Pinto-da-Rocha et al, 2014;Bragagnolo et al, 2015). Even though species richness patterns and beta diversity of AF harvestmen have already been addressed in a previous publication (Pintoda-Rocha et al, 2005), that study was restricted to the south and south-east regions, excluding the north-east, which is the place where the AF is the least studied and the most threatened.…”

The disjunct pattern of the Neotropical harvestman Discocyrtus dilatatus (Gonyleptidae) explained by climate-driven range shifts in the Quaternary: Paleodistributional and molecular evidence

“…The phylogeographic analysis may help to uncover evolutionary events at the species level, such as habitat fragmentation, range expansion, migration, vicariance or lineage extinction. Several contributions have already demonstrated the usefulness of this methodological approach to tackle biogeographic questions in harvestmen [ 48 – 52 ]. In this paper, an integrated SDM / phylogeographic approach is proposed to evaluate the historical scenarios invoked to explain the disjunct pattern of D .…”