Summary Aldrovanda vesiculosa is an aquatic carnivorous plant native to nutrient impoverished wetland systems in Australia, Africa, Asia, and continental Europe that has declined dramatically throughout its native range in the last century. A strong reliance upon carnivory generally limits its occurrence to specific, nutrient‐poor, island‐like microhabitats. Remaining native populations are generally small and fragmented, and empirical population ecology data for the species arelacking. Developing an understanding of the constraints to growth, establishment and reproduction in A. vesiculosa is crucial to conservation of the species. In contrast with the decline of the species throughout its native range, a number of large A. vesiculosa populations have become naturalised in North America. This study examines the population ecology of A. vesiculosa at one of these naturalised sites and assesses the species' potential invasiveness in terms of its ecological characteristics. Transect and quadrat surveys were used to determine the response of morphology, fecundity and spatial distribution to putative biotic and environmental variables, with glasshouse trials and a bird feeding experiment employed to test the persistence of seeds in the seed bank and after transport in bird guts. Although A. vesiculosa is capable of becoming locally abundant (up to 1260 individuals m−2) in wetland areas where biotic and abiotic conditions are optimal, it appears to compete poorly with floating and emergent macrophytes and is limited predominantly to specific microhabitats. The ecological characteristics of A. vesiculosa suggest that it poses a low invasion risk. The species' growth and reproductive potential are highest in shallow areas harbouring loose vegetation assemblages, with over two thirds of all individuals recorded from water 10–50 cm in depth and in areas with <50% native macrophyte cover. Seeds are unlikely to play a significant role in seasonal persistence or dispersal, with poor floral success (c. 10%), few seeds produced, low seed viability (<50%) throughout the study area and no seeds recovered from the sediment seed bank or recovered from bird faeces following gut transport. The stenotopic ecology of A. vesiculosa, and the continuing decline of dystrophic freshwater wetlands globally, indicate that remaining natural populations are highly sensitive and are likely to decline rapidly without adequate management. In addition to wetland management at the catchment scale to mitigate processes such as eutrophication, future conservation and reintroduction initiatives for A. vesiculosa must focus particularly on the identification, maintenance and restoration of optimal shallow humic microsites harbouring loose, open assemblages of emergent and floating macrophytes.

Background and aims Little is known about the evolutionary and ecological drivers of carnivory in plants, particularly for those terrestrial species that do not occur in typical swamp or bog habitats. The Mediterranean endemic Drosophyllum lusitanicum (Drosophyllaceae) is one of very few terrestrial carnivorous plant species outside of Australia to occur in seasonally dry, fire-prone habitats, and is thus an ecological rarity. Here we assess the nutritional benefits of prey capture for D. lusitanicum under differing levels of soil fertility in situ. Methods We measured the total nitrogen and stable nitrogen and carbon isotope ratios of D. lusitanicum leaves, neighbouring non-carnivorous plant leaves, and groups of insect prey in three populations in southern Spain. We calculated trophic enrichment (ε15N) and estimated the proportion of prey-derived nitrogen (%Nprey) in D. lusitanicum leaves, and related these factors to soil chemistry parameters measured at each site. Key results In all three populations studied, D. lusitanicum plants were significantly isotopically enriched compared with neighbouring non-carnivorous plants. We estimated that D. lusitanicum gain ~36 %Nprey at the Puerto de Gáliz site, ~54 %Nprey at the Sierra Carbonera site and ~75 %Nprey at the Montera del Torero site. Enrichment in N isotope (ε15N) differed considerably among sites; however, it was not found to be significantly related to log10(soil N), log10(soil P) or log10(soil K). Conclusions Drosophyllum lusitanicum individuals gain a significant nutritional benefit from captured prey in their natural habitat, exhibiting proportions of prey-derived nitrogen that are similar to those recorded for carnivorous plants occurring in more mesic environments. This study adds to the growing body of literature confirming that carnivory is a highly beneficial nutritional strategy not only in mesic habitats but also in seasonally dry environments, and provides insights to inform conservation strategies for D. lusitanicum in situ.

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