Ancestral States (ancestral + states)

Distribution by Scientific Domains
Distribution within Life Sciences

Selected Abstracts


EVOLUTION, Issue 5 2002
Bernard J. Crespi
Abstract The selective pressures involved in the evolution of semelparity and its associated life-history traits are largely unknown. We used species-level analyses, independent contrasts, and reconstruction of ancestral states to study the evolution of body length, fecundity, egg weight, gonadosomatic index, and parity (semelparity vs. degree of iteroparity) in females of 12 species of salmonid fishes. According to both species-level analysis and independent contrasts analysis, body length was positively correlated with fecundity, egg weight, and gonadosomatic index, and semelparous species exhibited a significantly steeper slope for the regression of egg weight on body length than did iteroparous species. Percent repeat breeding (degree of iteroparity) was negatively correlated with gonadosomatic index using independent contrasts analysis. Semelparous species had significantly larger eggs by species-level analysis, and the egg weight contrast for the branch on which semelparity was inferred to have originated was significantly larger than the other egg weight contrasts, corresponding to a remarkable increase in egg weight. Reconstruction of ancestral states showed that egg weight and body length apparently increased with the origin of semelparity, but fecundity and gonadosomatic index remained more or less constant or decreased. Thus, the strong evolutionary linkages between body size, fecundity, and gonadosomatic index were broken during the transition from iteroparity to semelparity. These findings suggest that long-distance migrations, which increase adult mortality between breeding episodes, may have been necessary for the origin of semelparity in Pacific salmon, but that increased egg weight, leading to increased juvenile survivorship, was crucial in driving the transition. Our analyses support the life-history hypotheses that a lower degree of repeat breeding is linked to higher reproductive investment per breeding episode, and that semelparity evolves under a combination of relatively high juvenile survivorship and relatively low adult survivorship. [source]

Connecting behaviour and performance: the evolution of biting behaviour and bite performance in bats

Abstract Variation in behaviour, performance and ecology are traditionally associated with variation in morphology. A neglected part of this ecomorphological paradigm is the interaction between behaviour and performance, the ability to carry out tasks that impact fitness. Here we investigate the relationship between biting behaviour and performance (bite force) among 20 species of ecologically diverse bats. We studied the patterns of evolution of plasticity in biting behaviour and bite force, and reconstructed ancestral states for behaviour and its plasticity. Both behavioural and performance plasticity exhibited accelerating evolution over time, and periods of rapid evolution coincided with major dietary shifts from insect-feeding to plant-feeding. We found a significant, positive correlation between behavioural plasticity and bite force. Bats modulated their performance by changing their biting behaviour to maximize bite force when feeding on hard foods. The ancestor of phyllostomids was likely a generalist characterized by high behavioural plasticity, a condition that also evolved in specialized frugivores and potentially contributed to their diversification. [source]

The Phylogenetic Significance of Anthropoid Paranasal Sinuses

James B. Rossie
Abstract In this study, the phylogenetic significance of anthropoid paranasal sinus anatomy is explored. New information reported in recent years has precipitated new hypotheses of sinus homology and more than doubled the number of anthropoid genera for which confident assessments of sinus identity can be made. As a result, it is likely that the phylogenetic meaning of commonly cited characters such as the ethmoid and frontal sinuses will change. The traditional method of "character mapping" is employed to test hypotheses of sinus homology and to reconstruct the ancestral states for sinus characters in major anthropoid clades. Results show that most sinuses appear to be primitive retentions in anthropoids, with their absences in various genera representing losses. Accordingly, many of these sinuses are potential anthropoid synapomorphies. Anat Rec, 291:1485,1498, 2008. 2008 Wiley-Liss, Inc. [source]

The evolution of conspicuous facultative mimicry in octopuses: an example of secondary adaptation?

The ,Mimic Octopus'Thaumoctopus mimicus Norman & Hochberg, 2005 exhibits a conspicuous primary defence mechanism (high-contrast colour pattern during ,flatfish swimming') that may involve facultative imperfect mimicry of conspicuous and/or inconspicuous models, both toxic and non-toxic (Soleidae and Bothidae). Here, we examine relationships between behavioural and morphological elements of conspicuous flatfish swimming in extant octopodids (Cephalopoda: Octopodidae), and reconstructed ancestral states, to examine potential influences on the evolution of this rare defence mechanism. We address the order of trait distribution to explore whether conspicuous flatfish swimming may be an exaptation that usurps a previously evolved form of locomotion for a new purpose. Contrary to our predictions, based on the relationships we examined, flatfish swimming appears to have evolved concurrently with extremely long arms, in a clade of sand-dwelling species. The conspicuous body colour pattern displayed by swimming T. mimicus may represent a secondary adaptation potentially allowing for mimicry of a toxic sole, improved disruptive coloration, and/or aposematic coloration. 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101, 68,77. [source]

Sensitivity analysis of different methods of coding taxonomic polymorphism: an example from higher-level bat phylogeny

CLADISTICS, Issue 6 2002
Nancy B. Simmons
New information concerning strengths and weaknesses of different methods of coding taxonomic polymorphisms suggests that results of some previous studies may have been unintentionally biased by the methods employed. In this study, we demonstrate that a form of sensitivity analysis can be used to evaluate the effects of different methods of coding taxonomic polymorphisms on the outcome of phylogenetic analyses. Our earlier analysis of higher-level relationships of bats (Mammalia: Chiroptera) employed superspecific taxa as terminals and scored taxonomic polymorphisms using ambiguity coding. Application of other methods of dealing with polymorphisms (excluding variable characters, inferring ancestral states, majority coding) to the same data yields phylogenetic results that differ somewhat from those originally reported based on ambiguity coding. Monophyly of some clades was supported in all analyses (e.g., Microchiroptera, Rhinopomatoidea, and Nataloidea), while other groups found to be monophyletic in the original study (e.g., neotropical Nataloidea) appeared unresolved or nonmonophyletic when other methods were used to code taxonomic polymorphisms. Several groupings that were apparently refuted in the initial study (e.g., Noctilionoidea including Mystacinidae) were supported in some analyses, reducing some of the apparent incongruence between the trees in our earlier analysis (which were based principally on morphology) and other trees based on molecular data. Perceived support for various groupings (branch support, bootstrap values) were in some cases significantly affected by the methods employed. These results indicate that sensitivity analysis provides a useful tool for evaluating effects of different methods of dealing with taxonomic polymorphism in superspecific terminal taxa. Variation in results obtained with different methods suggests that it is always preferable to sample at the species level when higher-level taxa exhibit taxonomic polymorphism, thus avoiding methodological biases associated with different methods of dealing with taxonomic polymorphisms during data analysis. [source]