Morphological variation of introduced passerines may indicate their adaptive directions of successful invasion
Sahar Firoozkoohi1, Adrian Paterson2, Jon Sullivan2
1Department of Pest-management and Conservation, Lincoln University, Lincoln, New Zealand (Sahar.Firoozkoohi@lincolnuni.ac.nz).
Introductions to new anthropogenic environments requires adaptive responses for a species to thrive and establish. New challenges include food resources, temperature, competition and predation. Comparative studies of phenotypic divergence of introduced species comparing n source and introduced populations, as well as between urban and rural populations, are little studied in New Zealand. We measured variation in locomotor related traits (e.g., wing, tarsus and tail morphology) and feeding-related traits (e.g., bill morphology and body mass) along a gradient from urban to rural and between the source (England) and introduced (New Zealand) populations of blackbirds (Turdus merula merula) and song thrushes (Turdus philomelos) from the Wellington and Canterbury regions. There were significant morphological differences in body mass of blackbirds with increasing body mass from urban to rural habitats. There were morphological differences in tarsus and tail lengths between New Zealand and the United Kingdom. The NZ population had shorter tails and tarsus length compared to the English population. Smaller locomotor morphological traits may be related to tendency of NZ populations to be sedentary, importance of flight distance, different predator pressures, sexual selection on tail length. Testing the intensity level of pollution, predator pressures, inter-and intra-specific competitions, connectivity and composition of landscape patches may highlight the intrinsic factors important in explaining variation between these populations. Studying morphological differences would help us to understand isolation forces processes that eventually lead to reinforcement and speciation between habitats.