Bergmann's rule and climate change revisited: Disentangling environmental and genetic responses in a wild bird population

Ecological Genetics Research Unit, Department of Biological and Environmental Sciences, PO Box 65, FI-00014 University of Helsinki, Helsinki, Finland.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 10/2008; 105(36):13492-6. DOI: 10.1073/pnas.0800999105
Source: PubMed

ABSTRACT Ecological responses to on-going climate change are numerous, diverse, and taxonomically widespread. However, with one exception, the relative roles of phenotypic plasticity and microevolution as mechanisms in explaining these responses are largely unknown. Several recent studies have uncovered evidence for temporal declines in mean body sizes of birds and mammals, and these responses have been interpreted as evidence for microevolution in the context of Bergmann's rule-an ecogeographic rule predicting an inverse correlation between temperature and mean body size in endothermic animals. We used a dataset of individually marked red-billed gulls (Larus novaehollandiae scopulinus) from New Zealand to document phenotypic and genetic changes in mean body mass over a 47-year (1958-2004) period. We found that, whereas the mean body mass had decreased over time as ambient temperatures increased, analyses of breeding values estimated with an "animal model" approach showed no evidence for any genetic change. These results indicate that the frequently observed climate-change-related responses in mean body size of animal populations might be due to phenotypic plasticity, rather than to genetic microevolutionary responses.

    • "This genetic basis for migration timing was also suggested for snow geese (Bety et al., 2004) and black-tailed godwits (Lourenç o et al., 2011), and may consequently also explain between-individual barnacle geese's variation in migration timing. Moreover, part of the observed repeatability might be phenotype plasticity (i.e. an environmentally based change in the phenotype) that lead to adaptation to the environmental condition (Teplitsky et al., 2008). "
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    ABSTRACT: tAccording to the green wave hypothesis, herbivores follow the flush of spring growth of forage plantsduring their spring migration to northern breeding grounds. In this study we compared two green waveindices for predicting the timing of the spring migration of avian herbivores: the satellite-derived greenwave index (GWI), and an index of the rate of acceleration in temperature (GDDjerk). The GWI was cal-culated from MODIS normalized difference vegetation index (NDVI) satellite imagery and GDDjerk fromgridded temperature data using products from the global land data assimilation system (GLDAS). To pre-dict the timing of arrival at stopover and breeding sites, we used four years (2008–2011) of tracking datafrom 12 GPS-tagged barnacle geese, a long-distance herbivorous migrant, wintering in the Netherlands,breeding in the Russian Arctic. The stopover and breeding sites for these birds were identified and therelations between date of arrival with the date of 50% GWI and date of peak GDDjerk at each site were ana-lyzed using mixed effect linear regression. A cross-validation method was used to compare the predictiveaccuracy of the GWI and GDDjerk indices. Significant relationships were found between the arrival datesat the stopover and breeding sites for the dates of 50% GWI as well as the peak GDDjerk (p < 0.01). The goosearrival dates at both stopover and breeding sites were predicted more accurately using GWI (R2cv= 0.68,RMSDcv= 5.9 and R2cv= 0.71, RMSDcv= 3.9 for stopover and breeding sites, respectively) than GDDjerk.The GDDjerk returned a lower accuracy for prediction of goose arrival dates at stopover ( R2cv= 0.45,RMSDcv= 7.79) and breeding sites (R2cv= 0.55, RMSDcv= 4.93). The positive correlation between the abso-lute residual values of the GDDjerk model and distance to the breeding sites showed that this index ishighly sensitive to latitude. This study demonstrates that the satellite-derived green wave index (GWI)can accurately predict the timing of goose migration, irrespective of latitude and therefore is suggestedas a reliable green wave index for predicting the timing of avian herbivores spring migration.
    Ecological Indicators 06/2015; 58:322-331. DOI:10.1016/j.ecolind.2015.06.005 · 3.23 Impact Factor
    • "), rather than simply a phenotypically plastic response to changing availability of resources (Gienapp et al., 2008). Furthermore, declines in body size are by no means universal (Meiri et al., 2009; Gardner et al., 2011, 2014a; Yom-Tov & Geffen, 2011): other studies have reported increases in size, and/or positive temperature–size correlations, and these in turn have frequently been interpreted as evidence of climate-driven changes in primary productivity that affect food or food quality (Gienapp et al., 2008; Teplitsky et al., 2008; Ozgul et al., 2010; Gardner et al., 2011, 2014b; Yom-Tov & Geffen, 2011). Such diversity between populations in the direction of associations makes it difficult to generalize as to the effects of climate change on morphology. "
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    ABSTRACT: Despite extensive research on the topic, it has been difficult to reach general conclusions as to the effects of climate change on morphology in wild animals: in particular, the effects of warming temperatures have been associated with increases, decreases or stasis in body size in different populations. Here, we use a fine-scale analysis of associations between weather and offspring body size in a long-term study of a wild passerine bird, the cooperatively breeding superb fairy-wren, in south-eastern Australia to show that such variation in the direction of associations occurs even within a population. Over the past 26 years, our study population has experienced increased temperatures, increased frequency of heatwaves and reduced rainfall - but the mean body mass of chicks has not changed. Despite the apparent stasis, mass was associated with weather across the previous year, but in multiple counteracting ways. Firstly, (i) chick mass was negatively associated with extremely recent heatwaves, but there also positive associations with (ii) higher maximum temperatures and (iii) higher rainfall, both occurring in a period prior to and during the nesting period, and finally (iv) a longer-term negative association with higher maximum temperatures following the previous breeding season. Our results illustrate how a morphological trait may be affected by both short- and long-term effects of the same weather variable at multiple times of the year and that these effects may act in different directions. We also show that climate within the relevant time windows may not be changing in the same way, such that overall long-term temporal trends in body size may be minimal. Such complexity means that analytical approaches that search for a single ‘best’ window for one particular weather variable may miss other relevant information, and is also likely to make analyses of phenotypic plasticity and prediction of longer-term population dynamics difficult.
    Global Change Biology 05/2015; DOI:10.1111/gcb.12926 · 8.22 Impact Factor
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    • "Nevertheless there is considerable debate about the mechanisms that underlie Bergmann's rule (Meiri et al. 2007, Stillwell 2010, Watt et al. 2010, Meiri 2011) and several authors have argued that climate-driven changes in primary productivity that affect an animal's net energy balance could equally account for observed global size patterns (Rosenzweig 1968, Geist 1987, McNabb 2010, Huston and Wolverton 2011). Indeed, the majority of studies conclude that contemporary changes in body size may result from changes in primary productivity that affect either food availability or food quality (Millien et al. 2006, Giennap et al. 2008, Teplitsky et al. 2008, Ozgul et al. 2009, 2010, Gardner et al. 2011, Sheridan and Bickford 2011, Yom-Tov and Geffen 2011, Teplitsky and Millien 2014). "
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    ABSTRACT: Alongside well researched shifts in species' distributions and phenology, reduction in the body size of organisms has been suggested as a third universal response to contemporary climate change. Despite mounting evidence for declining body size, several recent reviews highlight studies reporting increases in body size or no change over time. This variability in response may derive from the geographic scale of contributing studies, masking species-level responses to broad-scale environmental change and instead reflecting local influences on single populations. Using museum specimens, we examine temporal patterns of body size of 24 Australian passerine species, sampling multiple populations across the geographic ranges of each species between 1960 and 2007. Generalised additive models indictated that the majority (67%) of species showed important inter-annual body size variation, and there was striking cross-species similarity in temporal size patterns. Most displayed near-linear or linear, unidirectional size trends, suggesting a pervasive and directional change in environmental conditions, consistent with climate change. For species showing linear size responses, the absolute rate of size change ranged between 0.016 and 0.114% of body size (wing length) per year, consistent with studies on other continents. Overall, 38% (9/24) of species showed temporal declines in body size and 21% (5/24) showed increases, consistent with the variability and direction of size responses thus far documented among populations; declining body size is a pervasive response to climate change but it is not universal.
    Journal of Avian Biology 11/2014; 45(6). DOI:10.1111/jav.00431 · 2.24 Impact Factor
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