Zoology Departmental Seminar Series - Dr Karina Lucas Da Silva Brandao

Dr Karina Lucas Da Silva Brandao, Leibniz-Institut zur Analyse des Biodiversitätswandels

What we (un)know about Neotropical montane species of butterflies

A third of all terrestrial species on Earth are found in mountain habitats, which are hotspots for biodiversity mainly because of topographic variety, soil type heterogeneity, altitudinal gradients, and climatic variability. The great level of specialisation that montane organisms frequently display within limited temperature ranges is demonstrated by invertebrate montane species. Furthermore, it is anticipated that upslope migrations will reduce their possible area of occupancy and make them more susceptible to the stochastic extinctions that are typical of small populations. Climate change is a potential danger to the survival of these species that inhabit mountainous regions. This is especially true for the Brazilian Atlantic Forest, which has a high level of biodiversity but is now losing just 12% of its original vegetation due to habitat fragmentation brought on by urbanisation and human activity. 

Actinote butterflies (Nymphalidae, Heliconiinae, Acraeini) compose a small genus which has a highly distinctive wing pattern. The hindwing of every species has the similar striped pattern, yet different mimicry groups may be distinguished by colours and tones. Numerous Actinote species can be found in the mountains of the Brazilian Atlantic Forest, which is situated between 15° and 30° South and is primarily covered by tropical or subtropical forests. The climate varies in the interior (semi-deciduous forests with physiological drought and low mean temperature) to the interior (ombrophilous dense forests), which have no dry season. Montane speciation has been envisioned as a mechanism occurring through the evolution of the genus in this region.

In order to find a broad pattern of evolutionary mechanisms on these environments, we examined the population genomics patterns of two Actinote closely related highland species. Rather, we uncovered two disparate historical trends. Despite having a short, overlapping distribution that is thought to be connected to a chilly, humid environment, both butterfly species exhibit notable ecological differentiation: whereas one of them is found in wet forests above 1200 meters, has a slightly wider range, and feeds exclusively on one species of asteraceous vine, the other is found mostly above 1400 meters, prefers wet forests and contact zones with high altitude grasslands, and feeds on a few species of closely related shrubs. Despite the fact that both species exhibit a higher number of SNPs flagged for the LGM climate and it is thought likely that they expanded their range during cold and wet periods, the ecological specialisation indicates that the two species' detailed responses have likely differed and may have followed local microclimates, vegetation responses, or host plant responses. More in-depth conclusions are difficult since, of the hundreds of SNPs known for these species, only a very small number appear to be linked to climate.