Mountain Refugia Play a Role in Soil Arthropod Speciation on Madagascar: A Case Study of the Endemic Giant Fire-Millipede Genus Aphistogoniulus

Abstract

To elucidate the speciation mechanisms prevalent within hotspots of biodiversity, and the evolutionary processes behind the rise of their species-rich and endemic biota, we investigated the phylogeny of the giant fire-millipede genus Aphistogoniulus Silvestri, 1897, a Malagasy endemic. This study is the first comprehensive (molecular and morphological) phylogenetic study focusing on millipede (class Diplopoda) speciation on Madagascar. The morphological analysis is based on 35 morphological characters and incorporates ten described as well as two newly described species (A. rubrodorsalis n. sp. and A. jeekeli n. sp.) of Aphistogoniulus. The molecular analysis is based on both mitochondrial (COI and 16S), and nuclear genes (complete 18S rDNA), together comprised of 3031 base pairs, which were successfully sequenced for 31 individual specimens and eight species of Aphistogoniulus. In addition to the null-model (speciation by distance), two diversification models, mountain refugia and ecotone shift, were discovered to play a role in the speciation of soil arthropods on Madagascar. Mountain refugia were important in the speciation of the A. cowani clade, with three species occurring in the Andringitra and Ranomafana Mountains in the southeast (A. cowani), the Ambohijanahary and Ambohitantely Mountains in the mid-west (A. sanguineus), and the Marojejy Mountain in the northeast (A. rubrodorsalis n. sp.). An ecotone shift from the eastern rainforest to the unique subarid spiny forest of Mahavelo was discovered in the A. vampyrus - A. aridus species-pair. In the monophyletic A. diabolicus clade, evidence for divergent evolution of sexual morphology was detected: species with greatly enlarged gonopods are sister-taxa to species with normal sized gonopods. Among the large-bodied Spirobolida genera of Madagascar, Colossobolus and Sanguinobolus were found to be close sister-genera to Aphistogoniulus. Forest destruction has caused forest corridors between populations to disappear, which might limit the possible resolution of biogeographic analyses on Madagascar.

The millipedes collected by the Museum "La Specola" on Madagascar 1989/1991, with the description of three new species of giant pill-millipedes (Diplopoda, Sphaerotheriida, Arthrosphaeridae)

“…Order Spirobolida: Madagascar hosts the highest diversity of Spirobolida in the world, with a good degree of endemism (15 endemic genera, Wesener et al 2009, Wesener 2011. Aside from the previously recorded Trigoniulus corallinus, a widespread tramp (see Shelley 1998, Korsós 2004, Shelley et al 2006, one other common Spirobolida tramp species is recorded for the first time from Madagascar, Pseudospirobolellus avernus, as is the spirostreptid Glyphiulus granulatus.…”

A Phylogeographic Assessment of the Malagasy Giant Chameleons (Furcifer verrucosus and Furcifer oustaleti)

“…It is not unexpected that two different modes of divergence are supported within these sister groups since recent studies have shown multiple drivers of speciation in Madagascar [ 27 , 89 , 90 , 91 ]. It is interesting to note that the distributions of clades within F .…”

Four new species of the millipede genus Eutrichodesmus Silvestri, 1910 from Laos, including two with reduced ozopores (Diplopoda, Polydesmida, Haplodesmidae)

“…Wesener 2009; Car and Harvey 2014; Enghoff 2015), the problem of documenting millipede faunas is increasingly acute (Golovatch and Kime 2009). These localized occurrences make millipede species important subjects for biogeographic studies (Stoev and Enghoff 2003; Wesener et al 2010; Wesener et al 2011), but also put them at risk of local extinction from human activities such as forest destruction or large-scale mining operations (Wesener and Wägele 2007; Iniesta et al 2012). This holds especially true for Laos where the pace of forest destruction is alarmingly high (Gan et al 2016).…”