Montane speciation
The information gathered with the present genomic data and current distribution recovered a phylogeographic pattern that can be associated with the São Paulo subtropical gap (sensu Amaral et al., 2021), as a phylogeographic break for these montane butterflies. The role of the Atlantic Forest Mountain ranges in shaping the genetic structure of endemic species has already been observed for birds (Amaral et al., 2021; Thom et al., 2020). However, this is the first time that this pattern has been reported for an invertebrate. A previous study with the cold-associated bumblebees Bombus morio and B. pauloensis , which are mainly found in high- altitude areas of MAF, failed to recover a strong structured phylogeographic pattern (Françoso et al., 2016). However, the results of the demographic analyses and paleodistribution models are consistent with a scenario of expansion during the LGM.
The speciation between A. alalia and A. mantiqueiraprobably occurred recently during the Quaternary, considering that the divergence between these species and its sister species, A. catarina , was estimated around 3 million years ago, at the end of the Pliocene (Magaldi et al. in prep.). Pleistocene climatic oscillations have been hypothesized to have shaped the genetic structure of populations of other species currently found on the MAF (Amaral et al., 2021; Françoso et al., 2016; Thom et al., 2020).  Our results are consistent with paleoclimate, molecular, and pollen data obtained for other species, suggesting that the MAF taxa persisted or expanded during the LGM (Amaro et al., 2012; Carnaval et al., 2009; Leite et al., 2016). Accordingly, the ancestral populations of A. alalia and A. mantiqueira may have been limited to mountain tops several times in the past, yet they were likely able to explore currently unsuitable regions (mostly lowland) and hence expand their distribution during colder periods, which could have enabled a dispersal process to new mountain ranges (Paz et al., 2019). Mountain ranges provide diverse climatic conditions that allow montane species to adapt and survive the fluctuations in climate. This is made possible by the extensive variance in topography and altitudinal gradients (Brown Jr. & Ab’Saber, 1979). Furthermore, the low levels of genetic differentiation (as estimated by FST values) between the populations may not be due to high levels of current gene flow, but rather to this recent divergence (Palsbøll et al., 2004). Combining molecular and niche modeling data, we propose that Pleistocene climatic variation led to an allopatric and recent speciation process between the mountains of the Atlantic Forest.