Clutch Size Research Papers - Academia.edu (original) (raw)

Migration forms a significant part in the life cycle of temperate bird species. The regular movements appear to have originated in parallel with the postglacial northern expansion of tropical species, however, our knowledge is still poor regarding the early states and climatic backgrounds in the evolutionary history of migration. Nevertheless, this phenomenon is also influenced by several environmental and ecological factors, such as surviving inappropriate climatic conditions. Hence, understanding the origins and evolution of migratory behaviour requires integration of the biogeographic history and ecology of birds in a phylogenetic context. My aim was to find general conclusions in a wider taxonomic range, specifically: (1) to find climatic drivers of the biogeographic origin of the studied groups, (2) investigate the evolutionary origin of migration, and (3) several aspects of traits related to migration in these birds. I chose two well-studied, widely known, but phylogenetically distinct model groups of landbirds (Telluraves), similar in some aspects (e.g. diverse feeding ecology, reproductive biology, species with very limited distribution), but different enough for comparisons and contrasts. Therefore, I designed three studies applying comparative phylogenetic framework in each. First, molecular phylogenetic reconstruction and ancestral area estimation were performed to investigate historical biogeography in 179 accipitrid birds of prey (Accipitriformes). Ancestral state estimation, completed with correlated evolutionary analyses were applied to infer the origins and evolutionary changes in migratory behaviour in this group. Second, phylogenetic generalized least squares (PGLS) method was used to examine the relationships among distribution patterns, diet, hunting strategies, body measurements, clutch size, and migratory behaviour. Furthermore, maximum entropy modeling was applied to investigate the bioclimatic suitability of geographical ranges for migratory raptors. According to the results, migration evolved multiple times in birds of prey. One of the earliest events occurred in true hawks (Accipitrinae) during the Middle Miocene. In most cases, a tropical origin was inferred for the non-migratory ancestors of migratory lineages. Correlated evolutionary analyses indicate that migration evolved in the tropics, suggesting that temperate species might be descendants of tropical ones. Diet generalism is associated with migration among raptors. Moreover, clutch size and hunting strategies proved to be the most important variables in the three migratory systems. However, the geographic dissimilarities may mask important relationships between life history traits and migratory behaviours. Indeed, the European-African and the North-South American migratory systems are fundamentally different from the East Asian system, owing to the presence versus absence of ecological barriers. The second group of birds in the thirds study was the Turdidae (Passeriformes). Standard set of methods were used to build the phylogenetic tree of Turdidae, which is first published here. The above described approaches for raptors were also applied in Turdus thrushes to identify relationships between distribution patterns, diet, body measurements, clutch size, and migratory behaviour. The main biogeographic models (DIVA, DEC, BayArea) were compared to infer historical biogeographic within the group. The results show that the most probable ancestor regions for all 72 Turdus species were located in the East Palearctic and/or Afrotropical realms. Several trans-Atlantic movements occurred between 11-4 Mya, including the earliest events found to date. Migration emerged as an ancestral behaviour of the genus. Clutch size and main food types are associated with migratory behaviour. Correlated evolution between migration and along-latitudinal mobility, main food type, and the shift in main food type between seasons show high importance. Along-latitudinal movements may have evolved earlier, simultaneously with the radiations of Turdus thrushes, followed by the appearance of north-south migration, in connection with the orographic and climatic changes. The increased clutch sizes observed in migratory species could be important mechanism to compensate losses to mortality during migration. The results of bioclimatic analyses imply possible conservation applications and predict the need of attention to important patterns in changes of distribution and population trends in small passerines. Finally, the generalisation of my findings can be summarised as follows. (1) The southern origin of core landbirds is supported by the historical biogeographic analyses of the studied groups. (2) The hotspot nature of Southeast Asia and Africa is confirmed, thus South America could be an early destination rather than the source of origin. (3) The emergence of grassland vegetation and hence the shift in forested habitats provided novel niches available during the Late Miocene which accelerated the diversification of both Accipitriformes and Turdidae, similarly to a general pattern in all birds. (4) Recent bioclimatic conditions showed several limiting factors, mostly related to temperature that have equal impacts on birds’ behaviour on both of their breeding and wintering areas. (5) The differences in the geographically identifiable migratory systems are related to the connectivity of the distribution of species. (6) The result of maximum entropy modeling may show significant signs for predicted population changes in passerine birds. (7) Migration evolved multiple times, independently in raptors from non-migratory ancestors, whilst thrushes originated from migratory ancestors, which is a substantial difference in the origin of migration between the two groups. (8) Migratory behaviour seems to be more facultative among accipitrid raptors, however, in Turdus thrushes, migration might be a heritage rooting in the ‘alonglatitudinal’ mobility of ancestors. (9) Migration could have evolved in species with higher plasticity in diet or on the other way around. Either being a generalist (larger diet breadth in some raptor species or the omnivory of thrushes), or being able to easily adapt to different food sources (change in main food type in thrushes) are highly associated with migratory lineages. (10) Migratory birds suffer from higher mortality during migration, which can be observed as increased numbers in clutch sizes that may be an evidence for the trade-off between migration and reproduction/survival. This phenomenon could have appeared multiple times, phylogenetically independently.