Habitat segregation among mimetic ithomiine butterflies (Nymphalidae)

Abstract

The extensive wing pattern diversity observed among sympatric unpalatable mimetic butterflies is difficult to explain. Diversity is a paradox because selection by predators is expected to drive local species to use the same aposematic patterns. Habitat segregation among mimicry complexes has been suggested as a hypothesis to explain how diversity could be maintained. However, very few studies have tested this hypothesis. To test whether mimicry complexes are associated with particular habitats, I sampled a diverse assemblage of ithomiine butterflies from eastern Ecuador comprising nine discrete mimicry complexes. Butterflies were sampled in four habitats varying along a gradient of succession. A total of 43 species and 902 individuals were sampled. Ithomiine species richness and abundance were lowest in open habitats, and habitat preferences were documented for many species. Mimicry complexes exhibited significant habitat differences supporting the role of habitat segregation in maintaining mimetic diversity. However, there was obvious overlap among mimicry complexes, particularly involving the two numerically dominant patterns at the site. The pattern of segregation appears to be driven by common species, with relatively little evidence that the distribution of rarer species matches that of the more abundant species. Thus, habitat segregation is likely to play a role in the evolution of mimetic diversity as a result of segregated abundant model species, but the effect is probably weak and other factors are also important.

Heterogeneity in predator micro-habitat use and the maintenance of Müllerian mimetic diversity

“…If this increased association had been due to constraints on niche divergence among co-mimics, or solely to evolution of mimicry pattern, we would have expected reduced niche evolution (for constraints on niche divergence) or similar rates of niche evolution (for only mimicry evolution) for heterogeneous predator micro-habitat use relative to homogeneous micro-habitat use. Concordant heterogeneity in the micro-habitat use of predator and prey species has been detected in neotropical communities of avian predators and unpalatable ithomiine butterflies (Willmott et al unpublished results), with the latter possessing substantial local inter-specific diversity of mimetic forms (Beccaloni, 1997a;DeVries et al, 1999;Elias et al, 2008;Hill, 2010). Our theoretical results provide a potential explanation for these empirical data, namely that an initial heterogeneous predator distribution has driven this heterogeneous distribution of unpalatable prey with different mimetic patterns by acting as a selective force favoring niche convergence among co-mimics.…”

“…This hypothesis may explain, for example, the persistence of multiple mimicry rings within ithomiine butterfly communities. Differences in micro-habitat use have been detected among members of different ithomiine mimicry rings (Beccaloni, 1997b;DeVries et al, 1999;Elias et al, 2008;Hill, 2010), linked to host-plant distribution (Willmott and Mallet, 2004). Moreover, evidence suggests that avian insectivores partition micro-habitats in a similar manner to mimetic butterflies (Willmott et al unpublished results).…”

Ecologically relevant cryptic species in the highly polymorphic Amazonian butterfly Mechanitis mazaeus s.l. (Lepidoptera: Nymphalidae; Ithomiini)

“…Given the likely significance of Mechanitis species in mimetic communities, a strong systematic foundation for the genus is important for further studies of the ecology and evolution of mimicry (e.g. Elias et al ., 2008; Hill, 2010).…”

Biodiversity Conservation and Phylogenetic Systematics

“…Co-mimetic ithomiines tend to share habitats (Chazot et al 2014 ). They also tend to share hostplants (Willmott and Mallet 2004 ), fl y at similar heights above the ground (Beccaloni 1997b ;Elias et al 2008 ) and fl y in similar forest microhabitats (DeVries et al 1999 ;Elias et al 2008 ;Hill 2010 ). These tightly-knit webs of interactions may thus be particularly sensitive to community disassembly caused by habitat or climate change (Sheldon et al 2011 ), with the potential for cascading co-extinctions due to the loss of a few species whose presence facilitates the existence of other species.…”