![]() In attempting to answer this question, we review current methods and highlight their limitations, as part of a more general attempt to propose best practice guidelines for studies of disparity. However, this example also highlights one of the greatest challenges confronting researchers who are attempting, increasingly, to obtain general insights from multiple independent studies: can the insights gained from studies using a diversity of methods, approaches and data types be considered equivalent? One of the most important insights is the discovery that morphological disparity is often greatest early in the evolutionary history of clades, indicating that capacity for evolutionary innovation wanes as clades age, which some have argued reflects the evolutionary assembly of gene regulatory networks that constrain later fundamental change. įundamental insights into evolutionary biology have been elicited from these four types of disparity analysis. It is one of the primary ways to investigate ecosystem functioning in palaeobiology when the study species (and their functional characteristics) are extinct. This approach has been used to investigate hypotheses of competitive replacement and changes in ecosystem function during and after mass extinctions. Traits can be linked to multiple functions and multiple functions can be linked to a single trait. The links between form and function, however, are not always clear. ![]() This approach assumes that groups with high disparity are also likely to be functionally and ecologically diverse and that groups found in similar regions of shape space will have similar functional and ecological roles. The disparity of a group can be used as a proxy for either the functional role it plays within an ecosystem or its ecological niche. ![]() Such multidimensional spaces (or morphospaces-defined broadly hereafter as a mathematical space relating morphological configurations generally based on some measure of similarity ) can then be used to tackle a diverse array of questions that can be grouped into four main (non-mutually exclusive) classes. taxa) can be placed in this space based on their trait values. Typically, methods to capture disparity are based on multidimensional spaces where each dimension represents an aspect of morphological variation (a trait) and biological observations (e.g. However, disparity analyses have since expanded into comparative biology as a means of capturing how intrinsic and extrinsic causal agents affect morphological evolution. Originally defined as ‘multidimensional morphological dissimilarity at a macroevolutionary scale’, the concept of disparity emerged from attempts by palaeobiologists to characterize the evolutionary origin of animal bodyplans and from attempts by comparative developmental biologists to provide causal explanations for their emergence. These phenomena suggest that taxonomic diversity and phenotypic disparity are not inextricably linked, raising important questions, such as: how does disparity evolve? Are some morphologies more common than others? Is anatomical evolution unbounded or are some anatomies impossible to achieve? What role does ecology play in structuring disparity? Analyses of species diversity have a venerable history, but those of disparity are comparatively more recent. afrotherian mammals) or depauperate in both species diversity and disparity (e.g. rodents or nematodes), species-poor but rich in disparity (e.g. cichlids or molluscs), species-rich but disparity-poor (e.g. At the extremes, clades may be exceptionally rich in species and phenotypic diversity (hereafter disparity) (e.g. ![]() Clades of organisms are characterized by variation in both numbers of species and range of phenotypes through time. ![]()
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