Exploring the evolutionary dynamics of myrmecophytism: Perspectives from the Southeast Asian Macaranga ant-plant symbiosis.

Myrmecophytic plants utilise defensive services offered by obligate ant partners nesting in their domatia in a novel means of survival in tropical habitats. Although much is known about the ecology of myrmecophytism, there aren't enough empirical examples to demonstrate whether it substantially influences evolutionary patterns in host plant lineages. In this study, we make use of the species-rich Macaranga (Euphorbiaceae) ant-plant symbiosis distributed in the Southeast Asian Sundaland to delve into the evolutionary dynamics of myrmecophytism in host plants. We generated the most comprehensive dated phylogeny of myrmecophytic Macaranga till date using genotyping-by-sequencing (GBS). With this in hand, we traced the evolutionary history of myrmecophytism in Macaranga using parametric biogeography and ancestral state reconstruction. Diversification rate analysis methods were employed to determine if myrmecophytism enhanced diversification rates in the genus. Our results demonstrate that myrmecophytism is labile and easily lost. Ancestral state reconstruction supported a single origin of myrmecophytism in Macaranga âˆ¼18 mya on Borneo followed by multiple losses. Diversification rate analysis methods did not yield sufficient evidence to support the hypothesis that myrmecophytism enhanced diversification rates in Macaranga; we found that topographical features on Borneo may have played a more direct role in the divergence of clades instead. Our study provides evidence that while the acquisition of domatia clearly functions as a key innovation that has enabled host plants to exploit the environment in novel ways, it may not necessarily enhance diversification rates. In fact, we hypothesise that overly specialised cases of myrmecophytism may even be an evolutionary dead end.

No evidence for effects of infection with the amphibian chytrid fungus on populations of yellow-bellied toads.

The parasitic chytrid fungus Batrachochytrium dendrobatidis (Bd) can cause the lethal disease chytridiomycosis in amphibians and therefore may play a role in population declines. The yellow-bellied toad Bombina variegata suffered strong declines throughout western and northwestern parts of its range and is therefore listed as highly endangered for Germany and the federal state of Hesse. Whether chytridiomycosis may play a role in the observed local declines of this strictly protected anuran species has never been tested. We investigated 19 Hessian yellow-bellied toad populations for Bd infection rates, conducted capture-mark-recapture studies in 4 of them over 2 to 3 yr, examined survival histories of recaptured infected individuals, and tested whether multi-locus heterozygosity of individuals as well as expected heterozygosity and different environmental variables of populations affect probabilities of Bd infection. Our results show high prevalence of Bd infection in Hessian yellow-bellied toad populations, but although significant decreases in 2 populations could be observed, no causative link to Bd as the reason for this can be established. Mass mortalities or obvious signs of disease in individuals were not observed. Conversely, we show that growth of Bd-infected populations is possible under favorable habitat conditions and that most infected individuals could be recaptured with improved body indices. Neither genetic diversity nor environmental variables appeared to affect Bd infection probabilities. Hence, genetically diverse amphibian specimens and populations may not automatically be less susceptible for Bd infection.

Isolation and characterization of 11 new microsatellite markers for Macaranga (Euphorbiaceae).

We provide primer sequences for 11 new polymorphic microsatellite markers developed in the tropical ant-plant genus Macaranga (Euphorbiaceae), after enrichment cloning of Macaranga tanarius and Macaranga hypoleuca. Allele numbers per locus ranged from two to 16 among 20 accessions of M. tanarius, and from three to 10 among 22 accessions of M. hypoleuca. Observed and expected heterozygosities ranged from 0.150 to 0.900 and from 0.375 to 0.894 in M. tanarius, and from 0.545 to 1.000 and from 0.434 to 0.870 in M. hypoleuca, respectively. Six of the 11 primer pairs successfully cross-amplified polymorphic polymerase chain reaction products in Macaranga winkleri.

Single nucleotide sequence analysis: a cost- and time-effective protocol for the analysis of microsatellite- and indel-rich chloroplast DNA regions.

We present a simple method to screen for DNA sequence variation in microsatellite- and indel-rich regions of the chloroplast genome. The single nucleotide sequence (SNS) analysis provides a trade-off between the time- and cost-effective, but less informative and homoplasy-sensitive electrophoretic detection of microsatellite and indel size variation on the one hand, and more costly, but also more accurate methods like DNA sequencing on the other. The principle of the SNS method is to sequence one instead of all four nucleotides of a target region amplified by polymerase chain reaction. By careful selection of the respective nucleotide, almost the same amount of information can be retrieved from these partial sequences as could be from complete sequences; however, only a third to a fourth of the money and time resources are needed.