Global warming is modifying the phenology, life-history traits and biogeography of species around the world. Evidence of these effects have increased over recent decades; however, we still have a poor understanding of the possible outcomes of their interplay across global climatic gradients, hindering our ability to accurately predict the consequences of climate change in populations and ecosystems. We examined the effect that changes in biogeography can have on the life-history traits of two of the most successful range-extending fish species in the world: the tropical rabbitfishes Siganus fuscescens and Siganus rivulatus. Both species have established abundant populations at higher latitudes (poleward) in the northern and southern hemispheres and have been identified as important ecological engineers with the potential to alter the community structure of seaweed forests (Laminariales and Fucales) in temperate regions. Life-history trait information from across their global distribution was compiled from the published literature and meta-analyses were conducted to assess changes in (i) the onset and duration of reproductive periods, (ii) fecundity, (iii) size at maturity, (iv) growth rates, (v) maximum body sizes and (vi) longevity in populations at the leading edge of range expansion in relation to sea surface temperature and primary productivity (i.e., a common proxy for nutritional resource levels). Populations at highest latitudes had shortened their reproductive periods and reduced growth rates, taking longer to reach sexual maturity and maximum sizes, but compensated this with higher fecundity per length class and longer lifespans than populations in warmer environments. Low primary productivity and temperature in the Mediterranean Sea resulted in lower growth rates and body sizes for S. rivulatus, but also lower length at maturity, leading to increased life-time reproductive output. The results suggest that plasticity in the phenology and life-history traits of range-expanding species would be important to enhance their fitness in high latitude environments, facilitating their persistence and possible further poleward expansions. Quantifying the magnitude and direction of these responses can improve our understanding and ability to forecast species redistributions and its repercussions in the functioning of temperate ecosystems. 

Quantitative information was obtained from the literature using the following two independent search criteria in the Web of Science: {*Siganus OR rabbitfish* AND *reproduction OR fecundity OR spawning*} and {*Siganus OR rabbitfish* AND *size OR length OR growth OR Age OR abundance*}. Publications with useful information were then selected, and the references cited within, as well as the publications that had cited each of these works, were reviewed in turn to obtain more publications that were not detected by the initial online searches. Siganus fuscescens and Siganus canaliculatus were considered synonyms and data from studies of these were pooled (Hsu et al. 2011). Data were extracted from tables and scatterplot figures using the software DataThief (Flower et al. 2016). In all cases, length was standardized to fork length (FL) using the length-length equations reported in FishBase for S. fuscesens (Froese & Pauly 2019), and by Shakman et al. (2008) for S. rivulatus. Information on growth and longevity for both species of rabbitfish was only extracted from studies that reported growth curves based on length-at-age information produced from the analysis of sectioned sagittal otoliths of females and males. In addition, we estimated length-at-age information for populations of S. fuscescens in Western Australia from specimens collected in temperate (Perth) and tropical environments (Pilbara and Kimberley).