Our ability to predict invasions has been hindered by the seemingly idiosyncratic contextdependency of individual invasions. However, we argue that robust and useful generalisations in invasion science can be made by considering ''invasion syndromes'' which we define as ''a combination of pathways, alien species traits, and characteristics of the recipient ecosystem which collectively result in predictable dynamics and impacts, and that can be managed effectively using specific policy and management actions''. We describe this approach and outline examples that highlight its utility, including: cacti with clonal fragmentation in arid ecosystems; small aquatic organisms introduced through ballast water in harbours; large ranid frogs with frequent secondary transfers; piscivorous freshwater fishes in connected aquatic ecosystems; plant invasions in high-elevation areas; tall-statured grasses; and tree-Electronic supplementary material The online version of this article (

Management of biological invasions increasingly relies on the knowledge of invasive species' dispersal pathways that operate during introduction and post-introduction dispersal. However, the early stages of biological invasions (introduction, establishment, and initial spread) are usually poorly documented, limiting our understanding of postintroduction dispersal and the role of humans in invasive spread. We aim to assess a new approach to retrospectively understand spatio-temporal patterns of introduction, establishment, dispersal, and spread in biological invasions, using the case study of an ongoing invasion of the Indian bullfrog (Hoplobatachus tigerinus) on the Andaman archipelago, Bay of Bengal. We sampled 91 villages on eight human inhabited islands of the Andaman archipelago from 2015 to 2016. We assessed the occurrence of the bullfrog using visual encounter surveys and recorded the invasion history (year of establishment, source site, and dispersal pathway) for each site by surveying 892 key informants (farmers, plantation workers, and aqua-culturists). We sought to corroborate the reconstructed invasion history with false positive occupancy modelling, using site specific covariates that corresponded to hypotheses on specific dispersal pathways. The bullfrog occurred in at least 62% of the sampled sites spread over six islands, a dramatic increase to the previously known invaded range. The bullfrog was most likely introduced in early 2000s, and its exponential expansion has occurred since 2009. 'Contaminants' of fish culture trade and intentional 'release' were reported to be the primary pathways of introduction and post-introduction dispersal, facilitating introductions from the Indian mainland and interisland transfers. False-positive occupancy modelling confirmed that three sites on the archipelago influenced the invasion disproportionately by acting as dispersal hubs. The study elucidates the efficacy of using public surveys to identify dispersal pathways and hubs, and to understand invasive spread, when such information is typically unavailable otherwise. The proposed approach is scalable to other systems and species.

The burgeoning global pet trade in vertebrates, including amphibians, has conservation implications for overexploitation of native populations, spread of diseases, and invasions. The majority of amphibian invasions are due to the pet trade pathway and current lists of extra-limital amphibians suggest that future invasions will encompass a broader taxonomic diversity than is known. Given that trade is dynamic, it is essential to move beyond currently traded species and understand which species are likely to be traded in the future and serve as candidates for invasions. In this study, we systematically assess amphibian species in the pet trade, (i) characterising taxonomic bias, (ii) evaluating species-traits as predictors of traded species and trade volume, and (iii) forecasting likely future pets. We collated a global list of 443 traded amphibians and a regional dataset (USA) on trade volume. Species-traits (body size, native range size, clutch size, and breeding type) and conservation status, were considered as predictors of traded species and volume. Six Families contributed disproportionately to the amphibian pet trade; the likelihood for species to be traded was positively associated with body size, range size, and a 'larval' breeding type. However, species-traits performed poorly in predicting trade volume, suggesting an overriding effect of socio-economic aspects of the trade. The identified species-traits and taxonomic bias of the trade were then used to predict species likely to be traded as pets in the future. This study formalizes the knowledge on amphibian species that are traded as pets. We found a strong bias for certain Families, along with a preference for large-bodied and widely distributed species with a larval phase. Our results pave way for more traitbased approaches to forecast amphibians entering the trade. Such understanding of the pet trade can help pre-emptively tackle the pathway responsible for most invasions and disease spread in amphibians.

Island ecosystems have traditionally been hailed as natural laboratories for examining phenotypic change, including dramatic shifts in body size. Similarly, biological invasions can drive rapid localized adaptations within modern timeframes. Here, we compare the morphology of two invasive guttural toad ( Sclerophrys gutturalis ) populations in Mauritius and Réunion with their source population from South Africa. We found that female toads on both islands were significantly smaller than mainland counterparts (33.9% and 25.9% reduction, respectively), as were males in Mauritius (22.4%). We also discovered a significant reduction in the relative hindlimb length of both sexes, on both islands, compared with mainland toads (ranging from 3.4 to 9.0%). If our findings are a result of natural selection, then this would suggest that the dramatic reshaping of an amphibian's morphology—leading to insular dwarfism—can result in less than 100 years; however, further research is required to elucidate the mechanism driving this change (e.g. heritable adaptation, phenotypic plasticity, or an interaction between them).

Sleeping exposes lizards to predation. Therefore, sleeping strategies must be directed towards avoiding predation and might vary among syntopic species. We studied sleeping site characteristics of two syntopic, congeneric lizards -the Bay Island forest lizard, Coryphophylax subcristatus and the short-tailed Bay Island lizard, C. brevicaudus and evaluated inter-specific differences. We measured structural, microclimatic and potential predator avoidance at the sleeping perches of 386 C. subcristatus and 185 C. brevicaudus.Contrary to our expectation, we found similar perch use in both species. The lizards appeared to use narrow girth perch plants and accessed perches by moving both vertically and horizontally. Most lizards slept on leaves, with their heads directed towards the potential path of a predator approaching from the plant base. There was no inter-specific competition in the choices of sleeping perches. These choices indicate an anti-predator strategy involving both tactile and visual cues. This study provides insight into a rarely studied behaviour in reptiles and its adaptive significance. 46 with their heads directed towards the potential path of a predator approaching from the plant 47 base. There was no inter-specific competition in the choices of sleeping perches. These choices 48 indicate an anti-predator strategy involving both tactile and visual cues. This study provides 49 insight into a rarely studied behaviour in reptiles and its adaptive significance.