Calls, colours, shape, and genes: a multi-trait approach to the study of geographic variation in the Amazonian frog Allobates femoralis

Abstract

Evolutionary divergence in behavioural traits related to mating may represent the initial stage of speciation. Direct selective forces are usually invoked to explain divergence in mate-recognition traits, often neglecting a role for neutral processes or concomitant differentiation in ecological traits. We adopted a multi-trait approach to obtain a deeper understanding of the mechanisms behind allopatric divergence in the Amazonian frog, Allobates femoralis. We tested the null hypothesis that geographic distance between populations correlates with genetic and phenotypic divergence, and compared divergence between mate-recognition (acoustic) and ecological (coloration, body-shape) traits. We quantified geographic variation in 39 phenotypic traits and a mitochondrial DNA marker among 125 individuals representing eight populations. Geographic variation in acoustic traits was pronounced and tracked the spatial genetic variation, which appeared to be neutral. Thus, the evolution of acoustic traits tracked the shared history of the populations, which is unexpected for pan-Amazonian taxa or for mate-recognition traits. Divergence in coloration appeared uncorrelated with genetic distance, and might be partly attributed to local selective pressures, and perhaps to Batesian mimicry. Divergence in body-shape traits was low. The results obtained depict a complex evolutionary scenario and emphasize the importance of considering multiple traits when disentangling the forces behind allopatric divergence.

The Value of Including Intraspecific Measures of Biodiversity in Environmental impact Surveys is Highlighted by the Amazonian Brilliant-Thighed Frog (Allobates Femoralis)

“…For example, A. femoralis has become a model organism for behavioral and communication research in this century. The existence of different call morphotypes has been pivotal to experiments investigating inter-population acoustic recognition [50], natural hybridization [32], acoustic signal evolution [28,51], and the information carried by distinct components of these signals [52]. The premature loss of one of these call morphotypes will undoubtedly leave an irreversible knowledge-gap that will affect many burgeoning research lines.…”

On the distinctive call of a threatened phenotype of Allobates femoralis (Anura: Aromobatidae) and its recognition by allopatric conspecific males

“…The characterization of A. femoralis advertisement calls recorded near Altamira adds to previous work that sampled the species' repertoire. It might influence future reappraisals of the species' biogeography (Amézquita et al, 2009) and sound signal evolution and its correlates (Santos et al, 2014), for which comprehensive data on intraspecific variation are desirable. Importantly, the recognition of the new, six-note call arrangement in the field led to concomitant DNA barcoding that associated this call morphotype to unique and distinct mitochondrial DNA haplotypes (Simões et al, 2014).The description presented in this study can therefore be used in the forthcoming years in monitoring programs to confirm whether the distribution of this lineage is restricted to forest remnants in or near sites impacted by the Belo Monte dam, on the Xingu River (Simões et al, 2014).…”

“…In this location, A. femoralis males emit calls formed by six notes, a pattern distinct from that of the typical, and geographically prevailing advertisement calls, formed by four notes (Amézquita et al, 2009;Simões et al, 2014). The evolutionary implications of call variation in A. femoralis from Altamira are vastly unknown, but no sharing of mitochondrial DNA haplotypes is detected between this group and other A. femoralis distributed in locations adjacent to the geographic boundaries of the Altamira region (Simões et al, 2014).…”

“…Variation in the number of notes that constitute each call has been reported for the species. However, calls tend not to vary in relation to note number within the same lineage or population (Amézquita et al, 2006(Amézquita et al, , 2009.…”

“…duration, bandwidth, peak frequency) of elements that constitute the acoustic signal, or more obvious shifts in composition of elements of call repertoire (Bee et al, 2001;Ryan & Rand, 2003;Boul et al, 2007;Guerra & Ron, 2008;Rodríguez et al, 2010). Although intraspecifi c variation of discrete elements occurs to some extent among acoustic signals of sympatric males of Neotropical anurans (e.g., Guerra & Ron, 2008;, fi xed diff erences have also been reported among allopatric groups of individuals, and these diff erences have been generally attributed to evolutionary eff ects of isolation by distance or vicariance, potentially reinforced by sexual selection (Boul et al, 2007;Guerra & Ron, 2008;Amézquita et al, 2009).…”