Feeding innovations in a nested phylogeny of Neotropical passerines

Abstract

One contribution of 15 to a theme issue 'Innovation in animals and humans: understanding the origins and development of novel and creative behaviour'. Several studies on cognition, molecular phylogenetics and taxonomic diversity independently suggest that Darwin's finches are part of a larger clade of speciose, flexible birds, the family Thraupidae, a member of the New World nine-primaried oscine superfamily Emberizoidea. Here, we first present a new, previously unpublished, dataset of feeding innovations covering the Neotropical region and compare the stem clades of Darwin's finches to other neotropical clades at the levels of the subfamily, family and superfamily/order. Both in terms of raw frequency as well as rates corrected for research effort and phylogeny, the family Thraupidae and superfamily Emberizoidea show high levels of innovation, supporting the idea that adaptive radiations are favoured when the ancestral stem species were flexible. Second, we discuss examples of innovation and problem-solving in two opportunistic and tame Emberizoid species, the Barbados bullfinch Loxigilla barbadensis and the Carib grackle Quiscalus lugubris fortirostris in Barbados. We review studies on these two species and argue that a comparison of L. barbadensis with its closest, but very shy and conservative local relative, the black-faced grassquit Tiaris bicolor, might provide key insights into the evolutionary divergence of cognition. A nested phylogeny of flexible new world birdsThe superfamily Emberizoidea, also known as New World nine-primaried oscines [1], includes the families Emberizidae, Icteridae, Parulidae and Cardinalidae, as well as Thraupidae, whose most famous members are Darwin's finches. The superfamily accounts for almost 8% of all birds (832 species, [2]) and has evolved a broad range of morphologies and feeding adaptations that have allowed it to radiate throughout the New World, parts of the Old World (buntings) and to colonize outlying islands in the Pacific (Galápagos finches, Cocos finch) and Atlantic oceans (Tristan da Cunha finches, Gough finch) [3]. The diversification rate of the superfamily, based on statistical comparisons [4] and molecular estimates of divergence time from common ancestors [1], is higher than that of other clades, with the families Icteridae (grackles, cowbirds and New World blackbirds) and Thraupidae (collectively referred to as tanagers) contributing most of the effect.The family Thraupidae in particular has a 40% higher diversification rate than its most closely related clades, five times higher than that of the Neoaves mean and an order of magnitude higher than the vertebrate average [1]. Recent revisions of Thraupidae molecular phylogeny [5] have led to the incorporation into this family of many species previously classified [6] as Emberizidae. This includes Darwin's finches, as well as several Caribbean bullfinch and grassquit genera, plus the bananaquit Coereba flaveola that had earlier been considered the sole member of the Coeribidae. This revision makes tanagers th...

Adaptable individuals and innovative lineages

“…Tebbich et al suggested that Darwin's finches might exemplify this pattern [40], and Lefebvre and colleagues reasoned that if that were right, the clade which contains Darwin's finches should show high rates of innovation, and members of the clade on other islands should likewise show high levels of individual adaptability. They confirmed both predictions [25]. A macroevolutionary pattern-adaptive radiation and high rates of populationlevel innovation-is explained by the characteristics of individual agents.…”

“…Likewise, Lefebvre et al recognize the role of predation threat in their choice of experimental models, choosing broad-niched island species, on the grounds that reduced predator threat makes these species more likely to innovate [25]. However, while a number of the papers in this volume discuss rates of innovation within different clades, and broad correlations between rates of innovation and morphological features (for example potential correlations between rates of technical innovation and brain size, see Navarrete et al [26]), and there is some discussion of whether innovation rates depend on ecological factors (in particular, on harsh environments) there is much less discussion of the relations between rates of innovation and broad geographical variables; for example, comparisons of island versus mainland species, or the relation between innovation rates and narrow versus broad geographical distribution.…”

Innovativeness as an emergent property: a new alignment of comparative and experimental research on animal innovation

“…2b in Lefebvre et al [91]). This is despite the Coeribinae showing high phenotypic variation in morphology and high diversification rates [93].…”

“…Dietary specialization would predict that Darwin's finches should have lower levels of innovations than would be expected relative to research effort. Clearly, more study is needed in the closely related, apparently highly innovative Thraupinae [91]. One should also bear in mind that the conclusions of comparative analyses, especially those that drill down to low taxonomic levels, are vulnerable to changes in phylogenetic classifications and yield very small numbers of innovations, reducing the power to identify patterns.…”

“…Lefebvre et al [91] provide the first test of the flexible stem hypothesis, which postulates that phenotypic plasticity is an ancient feature of some phylogenetic lineages [92]. The authors present an analysis of a new avian innovation dataset from the Neotropical region.…”