Higher evolutionary rates in life-history traits in insular than in mainland palms

Abstract

Isolated islands, due to the reduced interspecific competition compared to mainland habitats, present ecological opportunities for colonizing lineages. As a consequence, island lineages may be expected to experience higher rates of trait evolution than mainland lineages. However, island effects on key life-history traits of vascular plants remain underexplored at broad spatiotemporal scales, even for emblematic island clades such as palms. Here, we used phylogenetic comparative methods to evaluate potential differences in size and macroevolutionary patterns of height and fruit diameter among mainland, continental, and volcanic island palms. Further, phylogenetic beta-diversity was used to determine if lineage turnover supported an adaptive radiation scenario on volcanic islands. Volcanic island palms were taller than their continental island and mainland counterparts, whereas continental island palms exhibited smaller fruit size. Height and fruit size of palms evolved under evolutionary constraints towards an optimal value. However, scenarios of adaptive radiation and niche conservatism were not supported for the height and fruit size of volcanic and mainland palm clades, respectively, as expected. Instead, continental island palms exhibited higher evolutionary rates for height and fruit size. Insular palm assemblages (continental and volcanic) are composed of unique lineages. Beyond representing evolutionary sources of new palm lineages, our results demonstrate that insular habitats are important in shaping palm trait diversity. Also, the higher phenotypic evolutionary rates of continental island palms suggest disparate selection pressures on this habitat type, which can be an important driver of trait diversification over time. Taken together, these results stress the importance of insular habitats for conservation of functional, phylogenetic, and taxonomic diversity of palms.

Africa as an evolutionary arena for large fruits

“…This further suggests that conditions in Africa lifted constraints on fruit size evolution, possibly because both the largest and smallest fruits were able to persist (Mack, 1993). In addition to the Africa regime, other selective regimes or evolutionary, morphological or developmental constraints related to, for example, fruit colour, defence and island colonizations, have also contributed to palm fruit size evolution, both in Africa and elsewhere (Onstein et al ., 2017; Cássia‐Silva et al ., 2020; Nascimento et al ., 2020). This illustrates the complexity of understanding the selective pressures that have shaped the evolution of adaptive, functional traits, such as fruit size.…”

Macroecological links between the Linnean, Wallacean, and Darwinian shortfalls

“…Such a strong impact is largely due to the fact that the available diversification methods are sensitive to events occurring closer to the tips of phylogenies (see below). Indeed, when phylogenetic diversity metrics are applied in a geographical context (e.g., temperate vs. tropical comparisons), high uncertainty is introduced into the analyses, biasing our interpretations of how diversification processes drive diversity in these regions (Rabosky et al 2017;Schluter and Pennell 2017;Cássia-Silva et al 2020;Tietje et al 2022). In this context, the LTG (sensu Freeman and Pennell 2021) provides an interesting framework to explore how uneven knowledge about species taxonomy and geographical distribution may affect global diversification patterns.…”

The adaptive significance of large size at birth in marine snakes

“…For example, warm-climate species that extend their geographic range into cold climates may consistently respond via an evolutionary shift from oviparity to viviparity (in squamate reptiles [ 1 ]) or a reduction in clutch size (in birds [ 2 ]). Likewise, species that inhabit islands often exhibit different reproductive rates than do mainland taxa [ 3 , 4 ]. If multiple phylogenetic lineages make similar habitat transitions, we can assess the generality and causes of life-history changes induced by novel challenges in those new habitats.…”