Reversed Size Dimorphism in Raptors: Evidence for How It Evolved

Oikos ◽  
1988 ◽  
Vol 52 (1) ◽  
pp. 129 ◽  
Author(s):  
John M. Pleasants
Keyword(s):  
Size Dimorphism ◽  
Reversed Size Dimorphism

Mating Patterns and Reversed Size Dimorphism in Southern Skuas (Stercorarius skua lonnbergi)

The Auk ◽  
2002 ◽  
Vol 119 (3) ◽  
pp. 858-863
Author(s):  
Richard A. Phillips ◽  
Deborah A. Dawson
Keyword(s):  
Size Dimorphism ◽  
Mating Patterns ◽  
Reversed Size Dimorphism

The Reversed Size Dimorphism in Birds of Prey: A Reply

Oikos ◽  
1982 ◽  
Vol 38 (3) ◽  
pp. 388
Author(s):  
Ingvar N. Nilsson ◽  
Torbjörn von Schantz ◽  
Torbjorn von Schantz
Keyword(s):  
Birds Of Prey ◽  
Size Dimorphism ◽  
Reversed Size Dimorphism

scholarly journals Mating Patterns and Reversed Size Dimorphism in Southern Skuas (Stercorarius skua lonnbergi)

The Auk ◽  
2002 ◽  
Vol 119 (3) ◽  
pp. 858-863
Author(s):  
Richard A. Phillips ◽  
Deborah A. Dawson ◽  
Douglas J. Ross
Keyword(s):  
Sexual Selection ◽  
Assortative Mating ◽  
Confounding Factor ◽  
Foraging Strategies ◽  
Individual Quality ◽  
Territory Quality ◽  
Size Dimorphism ◽  
Mating Patterns ◽  
Reversed Size Dimorphism ◽  
Role Specialization

Abstract Numerous explanations exist for the evolution of reversed size dimorphism in raptorial species. A recent study concluded that reversed size dimorphism in skuas and jaegers was probably not attributable to breeding-role specialization, but that there was evidence for sexual selection, and in particular intrasexual competition by females for males. Our study tested the applicability of those conclusions for Southern (or Brown) Skuas (Stercorarius skua lonnbergi) breeding in South Georgia. Clutch volume was related positively to size and condition of females and negatively to condition of males, but there was no evidence of assortative mating for size or condition within pairs. Potential explanations for the discrepancy between this and previous studies are that size is less closely correlated with individual quality because of highly diverse foraging strategies, territory quality is a confounding factor, or because lower aggression in Southern Skuas reduces the necessity for small females to avoid large males.

Les conséquences de la reconnaissance des contraintes phylogénétiques lors de l'étude évolutive de l'origine des traits

1985 ◽  
Vol 63 (10) ◽  
pp. 2233-2239 ◽  
Author(s):  
François Chapleau
Keyword(s):  
Natural Selection ◽  
Theoretical Basis ◽  
Historical Context ◽  
Evolutionary Process ◽  
The Other ◽  
Theoretical Concepts ◽  
Size Dimorphism ◽  
Selective Pressures ◽  
Phylogenetic Studies ◽  
Reversed Size Dimorphism

This study examines the origin and consequences of the disregard of evolutionary biologists towards the historical constraints emerging from phylogenetic studies. An attempt is made to establish the theoretical basis that would allow the integration of these constraints in studies related to the understanding of evolutionary processes responsible for the origin of traits. First, the historical context is defined following the concepts of cladistic methodology. Then the empirical limits intrinsic to the structure of the theory of natural selection are outlined. Extrapolations of this evolutionary process at a historical level are not justifiable because of the impossibility of empirical verification. As a prerequisite for the study of species, it becomes essential to distinguish the autapomorphies (evolutionary novelties) from the plesiomorphies (primitive characters). Only the autapomorphies are potentially open to studies concerned with the ultimate causes related to their origin, since it is possible to gather the relevant data. On the other hand, since the selective pressures now affecting the plesiomorphies are not necessarily the same as those responsible for their origin, and since it is impossible to recreate the historical context in which they have originated, it is preferable that evolutionary biologists refrain from elaborating scenarios pertaining to the origin of those traits. A parallel is made between these two types of features and previous concepts of adaptation and exaptation. An example related to the origin of the "reversed" size dimorphism of the Falconiformes is used to illustrate these theoretical concepts.

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