Body size changes in passerine birds introduced to New Zealand from the UK

Abstract

One feature of global geographic variation in avian body sizes is that they are larger on isolated islands than on continental regions. Therefore, this study aims to assess whether there have been changes in body size following successful establishment for seven passerine bird species (blackbird Turdus merula, song thrush T. philomelos, house sparrow Passer domesticus, chaffinch Fringilla coelebs, greenfinch Chloris chloris, goldfinch Carduelis carduelis, yellowhammer Emberiza citrinella) introduced from the continental islands of the UK to the more isolated oceanic landmass of New Zealand in the middle of the nineteenth century. Measures of tarsus length were taken from individuals from contemporary UK and New Zealand populations of these species, and from historical specimens collected around the time that individuals were translocated from the UK to New Zealand. Analysis of Variance was used to test for size differences between contemporary UK and New Zealand populations, and between historical UK and contemporary UK and New Zealand populations. Historical UK populations have longer tarsi, on average, than 12 (7 UK and 5 New Zealand) of the 14 contemporary populations. Significant decreases in tarsus length relative to the historical populations have occurred in the UK for blackbird, chaffinch and greenfinch, and in the New Zealand blackbird population. Contemporary New Zealand house sparrows have significantly longer tarsi, on average, than both historical and contemporary UK populations. Exposure to novel environments may be expected to lead to changes in the morphology and other traits of exotic species, but changes have also occurred in the native range. In fact, contrary to expectations, the most common differences we found Blackburn et al. / NeoBiota 17: 1-18 (2013) 2 were between contemporary and historical UK populations. Consideration of contemporary populations alone would underestimate the true scale of morphological change in these species over time, which may be due to phenotypic plasticity or genetic adaptation to environmental changes experienced by all populations in the last 150 years.

Body size variation and caste ratios in geographically distinct populations of the invasive big-headed ant,Pheidole megacephala(Hymenoptera: Formicidae)

“…The interplay of body size and invasion success has been investigated in a biogeographical context in a variety of taxa (plants: Crawley, ; Thébaud & Simberloff, ; vertebrates: Veltman, Nee & Crawley, ; Jeschke & Strayer, ; Blackburn et al ., ; invertebrates: Lawton et al ., ; McGlynn, ; Miller, Hewitt & Ruiz, ; Roy, Jablonski & Valentine, ). In fact, differential investment into defence, growth or reproduction between native and introduced populations forms the basis for many hypotheses as to why introduced species are so successful in invaded areas (Blossey & Notzhold, ; Keane & Crawley, ; Shea & Chesson, ; Parker et al ., ).…”

Dialects of an invasive songbird are preserved in its invaded but not native source range

“…However, it can be the other way around because factors such as changes in land use in the native range can have a similar or even stronger influence than the novel environment. For example, morphological changes during the last ca 150 yr are in fact more apparent in British birds than in those introduced to New Zealand, with contemporary British yellowhammers being smaller than those in the mid‐19th century (Blackburn et al ). We argue that, in a similar vein, the most likely explanation for the observed differences in song dialects is that New Zealand yellowhammers have retained song structures that were present in both countries originally, but were lost from the source population in the UK subsequently.…”

“…Biological invasions can be a potential threat to the environment (Pyšek et al 2012, Kumschick et al 2015, Martin-Albarracin et al 2015 and economy (Pimentel et al 2005, Kettunen et al 2009), but they can also provide a golden opportunity to study evolutionary, behavioural or ecological phenomena on spatial and temporal scales unachievable by traditional experimental approaches (Hale and Briskie 2007, Yoshida et al 2007, Schrey et al 2011. Animal populations often differ between native and introduced ranges, in morphological (Blackburn et al 2013), lifehistory (Congdon and Briskie 2014) or behavioural traits (Pintor and Sih 2009), and biological invasions as 'natural experiments' can encompass vast areas, including whole continents (Norbury and Jones 2015), and several human generations (Lever 2005). Invasions may therefore provide insight into a range of natural phenomena.…”

Indirect evidence for body size reduction in a flightless island bird after human colonisation

“…In Australia, body size of snakes increased less than 70 years after the introduction of an invasive toad (Phillips and Shine 2004). Relatively rapid changes in body size have also been found in birds, as body size of birds introduced to New Zealand changed up to 4% within 150 years (Blackburn et al 2013). We think that, as the fossil bones of Kagu were leftovers in inhabited caves (Balouet and Olson 1989), the most likely reason for the body size reduction of Kagu was predation by humans.…”