Evolution in the introduced New Zealand populations of the common myna, Acridotheres tristis (Aves: Sturnidae)

Abstract

Common mynas were introduced into New Zealand from Australia in the 1870's. Seventy birds released at Wellington have apparently given rise to populations that now occur almost exclusively north of latitude 40° S. Morphometric variation in 28 characters of 307 adults was assessed statistically, based on eight samples spanning their New Zealand range. Univariate analysis revealed that 17 characters of males and 13 of females varied significantly among localities and that birds tend to be larger in the north. Discriminant analysis confirmed the north–south pattern of differentiation but disclosed that the newly established northern populations are very similar morphometrically. Both sexes have differentiated among localities in size and shape. Size variation is aligned with temperature only in males, and shape differences are associated with variation in precipitation in both sexes and altitude in females, females have differentiated in fewer characters than males, but overall, they show a stronger relationship between interlocality and intralocality character variability. Although the adaptive basis of increased size in warmer climates is unclear, the consistency of character covariation in localities with different climatic conditions argues against an ecophenotypic explanation. It is therefore concluded that the New Zealand populations are in the early stages of adaptive differentiation.

The biology of the stoat (Mustela erminea) in the National Parks of New Zealand III. Morphometric variation in relation to growth, geographical distribution, and colonisation

“…The range for New Zealand is 48.9-51.5 mm (difference 2.6 ± 0.45 mm; Table 5), and that for Western Europe is 46.8-49.6 mm (2.8 ± 0.33 mm) (Stubbe 1978); the ranges of size in the 2 areas were not significantly different (P > 0.1). This appears to be an instance of rapid morphological shift in a colonising species, certainly not a new phenomenon; it has been documented for sparrows by Johnston & Selander (1971) and Baker (1980), for mynas by Baker & Moeed (1979), and for feral cats by Derenne (1972). It is particularly interesting here because it has been so extensive, so clearly correlated with habitat, and-as for both mynas and sparrows-may have occurred differentially in the 2 sexes.…”

“…Variation in body size of the stoat in New Zealand could be of particular relevance to evolutionary ecology. As Baker & Moeed (1979) point out, studies of the extent and rate of morphological change in isolated populations of a species can provide critical evidence on the dynamic processes of evolution, and estimates of the rate of change are possible only in the few instances where the date of isolation is known.…”

GEOGRAPHIC VARIATION WITHIN AN ISLAND: UNIVARIATE AND MULTIVARIATE CONTOURING OF SCALATION, SIZE, AND SHAPE OF THE LIZARDGALLOTIA GALLOTI

“…comm.). Similarly, the pattern of between-group variation in body proportions in this and most other cases (e.g., Baker, 1980;Baker and Mooed, 1979;Selander, 1971, 1973;Fleischer and Johnston, 1982) has been interpreted in terms of selection even though the characters will be influenced by both genotype and environment. While one must bear in mind environmental influence, size and shape can be highly heritable (Atchley and Rutledge, 1980;Atchley et al, 1981), and the sexual dimorphism in size and shape in this case argues for a strong genetic influence.…”

“…This is an excessively great period of time against which to consider the cause of the present, relatively restricted patterns ofgeographic variation. Such geographic patterns can develop very quickly, i.e., in less than 100 years Selander, 1971, 1973;Baker, 1980;Baker and Mooed, 1979). Even the east-west patterns of speciation and incipient speciation in Europe due to Pleistocene events (Thorpe, 1979) may only be measured in tens or hundreds of thousands of years.…”

Morphometrics of forest birds in the Orongorongo Valley, Wellington, New Zealand

“…The extent to which the arrival of new species just over a century ago intensified interspecific competition probably cannot now be determined. But evolutionary adjustments are rapid, as shown by Baker & Moeed (1979) and Baker (1980) for introduced mynas and house sparrows, so morphological changes in native birds in New Zealand are likely to have occurred already, and may continue in the future.…”