Species diversity vs. morphological disparity in the light of evolutionary developmental biology
A. Minelli, Annals of Botany (2016).
Background: Two indicators of a clade’s success are its diversity (number of included species) and its disparity (extent of morphospace occupied by its members). Many large genera show high diversity with low disparity, while others such as Euphorbia and Drosophila are highly diverse but also exhibit high disparity. The largest genera are often characterized by key innovations that often, but not necessarily, coincide with their diagnostic apomorphies. In terms of their contribution to speciation, apomorphies are either permissive (e.g. flightlessness) or generative (e.g. nectariferous spurs).
Scope Except for Drosophila, virtually no genus among those with the highest diversity or disparity includes species currently studied as model species in developmental genetics or evolutionary developmental biology (evo-devo). An evo-devo approach is, however, potentially important to understand how diversity and disparity could rapidly increase in the largest genera currently accepted by taxonomists. The most promising directions for future research and a set of key questions to be addressed are presented in this review.
Conclusions From an evo-devo perspective, the evolution of clades with high diversity and/or disparity can be addressed from three main perspectives: (1) evolvability, in terms of release from previous constraints and of the presence of genetic or developmental conditions favouring multiple parallel occurrences of a given evolutionary transition and its reversal; (2) phenotypic plasticity as a facilitator of speciation; and (3) modularity, heterochrony and a coupling between the complexity of the life cycle and the evolution of diversity and disparity in a clade. This simple preliminary analysis suggests a set of topics that deserve priority for scrutiny, including the possible role of saltational evolution in the origination of high diversity and/or disparity, the predictability of morphological evolution following release from a former constraint, and the extent and the possible causes of a positive correlation between diversity and disparity and the complexity of the life cycle.
An evo-devo perspective on diversity and disparity Diversity (number of included species) and disparity (extent of morphospace occupied) are indicators of a clade’s success.
Genetic variation, habitat destruction and survival
Genetic variation, habitat destruction and survival
Divergent selection along climatic gradients in a rare endemic Selection, drift and gene flow shape genetic variation within and among natural populations and their study is important for conservation and evolutionary biology. Habitat destruction and fragmentation affect these processes by reducing the size and increasing the isolation of populations. Plants in small and isolated populations…
Coevolution Drives the Emergence of Complex Traits and Promotes Evolvability
by Luis Zaman, Justin R. Meyer, Suhas Devangam, David M. Bryson, Richard E. Lenski and Charles Ofria
"The evolution of complex organismal traits is obvious as a historical fact, but the underlying causes—including the role of natural selection—are contested. Gould argued that a random walk from a necessarily simple beginning would produce the appearance of increasing complexity over time. Others contend that selection, including coevolutionary arms races, can systematically push organisms toward more complex traits. Methodological challenges have largely precluded experimental tests of these hypotheses. Using the Avida platform for digital evolution, we show that coevolution of hosts and parasites greatly increases organismal complexity relative to that otherwise achieved. As parasites evolve to counter the rise of resistant hosts, parasite populations retain a genetic record of past coevolutionary states. As a consequence, hosts differentially escape by performing progressively more complex functions. We show that coevolution's unique feedback between host and parasite frequencies is a key process in the evolution of complexity. Strikingly, the hosts evolve genomes that are also more phenotypically evolvable, similar to the phenomenon of contingency loci observed in bacterial pathogens. Because coevolution is ubiquitous in nature, our results support a general model whereby antagonistic interactions and natural selection together favor both increased complexity and evolvability" (read more/open access).
***Haven't read it but I like these sorts of papers.
Evolution does not have foresight. But organisms with a greater capacity to evolve may fare better in changing environments. This raises the question: Does evolution favor characteristics that increase a species' ability to evolve? For several years, biologists have attempted to provide evidence that natural selection has acted on evolvability. Now a new article offers clear evidence that the answer is yes.
