Understanding the mechanisms of adaptation to spatiotemporal environmental variation is a fundamental goal of evolutionary biology. This issue also has important implications for anticipating biological responses to contemporary climate warming and determining the processes by which invasive species are able to spread rapidly across broad geographic ranges. Here, we compare data from a historical study of latitudinal variation in photoperiodic response among Japanese and U.S. populations of the invasive Asian tiger mosquito Aedes albopictus with contemporary data obtained using comparable methods. Our results demonstrated rapid adaptive evolution of the photoperiodic response during invasion and range expansion across ∼15° of latitude in the United States. In contrast to the photoperiodic response, size-based morphological traits implicated in climatic adaptation in a wide range of other insects did not show evidence of adaptive variation in Ae. albopictus across either the U.S. (invasive) or Japanese (native) range. These results show that photoperiodism has been an important adaptation to climatic variation across the U.S. range of Ae. albopictus and, in conjunction with previous studies, strongly implicate the photoperiodic control of seasonal development as a critical evolutionary response to ongoing contemporary climate change. These results also emphasize that photoperiodism warrants increased attention in studies of the evolution of invasive species.
Critical Photoperiods in US and Japanese Populations 1988 and 2008
Critical Photoperiods (cpp) for US and Japanese populations from 1988 are from Pumpuni (1989) and Focks et al. (1994). Critical photoperiods from US and Japanese populations are estimated from photoperiodic response curves as described in text. Country, j = japan, u=us.
Diapause incidence of US populations in 2008 estimated as described in text. Three letter opulation labels as in Table A1 of publication. Population labels for US populations from 2000 given as city and state. 2000 data are from Lounibos et al. 2003 as described in text of article.
female pupas mass
Female pupal mass (in milligrams) of populations from the US and Japan in the 2008 collection. Three letter population codes as in Table A1 of publication. jp= japan, us = United States.
female wing length
Female wing length (in millimeters) of populations from the US and Japan in the 2008 collection. Measurements performed as described in text of publication. Three letter population codes as in Table A1 of publication. jp= japan, us = United States.
Egg volume (in millimeters cubed x 10^-3) of populations from the US and Japan in the 2008 collection. Measurements performed as described in text of publication. Three letter population codes as in Table A1 of publication. jp= japan, us = United States.
Photoperiodic Response Curves
Photoperiodic response curves of US and Japanese populations from the 2008 collection. Percent diapause measured as described in text of publication. Each sheet provides the photoperiodic response of a single population, with seperate populations on seperate sheets. Three letter population codes as in Table A1.
photoperiodic response curve data.xlsx
Average date of first frost and average daily minima for weather stations located near collecting sites of populations from the US and Japan
The date of first frost and annual absolute minimum temperature from 1988-2008 were collected from the National Climatic Data Center (http://www.ncdc.noaa.gov/oa/ncdc.html) and the NOAA National Data Center (http://www7.ncdc.noaa.gov/CDO) for the US and Japan, respectively. For a location in which there were years that did not have a frost, the latest date of first frost across the 20 year data set for that particular population was substituted. For OKI, there was no frost date recorded for the 20 year data set; thus the latest date of first frost for all populations across all years was substituted
Blocking Design of CPP Experiment
Blocking design to measure photoperiodic response of populations from the US and Japan in the 2008 collection.