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The biogeography of predator‐induced defences is an understudied area of predator–prey dynamics. Range overlap with predators that induce the response and local demographics (e.g., prey abundances) are likely to be important factors for determining the biogeographic distribution of induced defences within species. However, with climate warming, range‐expanding warm‐water predators are increasingly preying upon temperate species. This is a consequence of a wider phenomenon known as tropicalisation. We aim to determine: (i) if individuals of a temperate barnacle with induced defences (‘bent morphs’) are primarily present where they co‐occur with range‐expanding warm‐water predators (muricid snails) and, (ii) if bent morphs are size‐structured within populations.

North‐eastern Pacific rocky intertidal zone (~26–40° N).

Tetraclita rubescens(Nilsson‐Cantell, 1931), Balanomorpha.

We use photoquadrats from sites across the range ofT. rubescensto determine the biogeographic distribution of populations with bent morphs and to assess size‐structure. We use a combination of field surveys, literature, and museum occurrences to assess range overlap between cool and warm‐water predators ofT. rubescensand their association with populations with bent morphs and abundance patterns ofT. rubescens.

Bent morphs are commonly found within the equatorward portion of the species' range (where abundances are highest), in populations overlapping with range‐expanding warm‐water predators. Bent morphs primarily occur within the smaller size classes.

To be partly resilient to the effects of tropicalisation, temperate prey must acclimatise/adapt to altered predator–prey dynamics. Predator‐induced defences are one way to do this. We show that bent morphs within a temperate prey species (T. rubescens) are largely restricted to populations that overlap with large‐bodied and range‐expanding warm‐water predators. This is evidence for the partial resilience ofT. rubescensto tropicalisation and provides the rationale for further exploration of the eco‐evolutionary consequences of tropicalisation in this study system and others.

Common taxonomic practices, which condition species' descriptions on diagnostic morphological traits, may systematically lump outcrossing species and unduly split selfing species. Specifically, higher effective population sizes and genetic diversity of obligate outcrossers are expected to result less reliable phenotypic diagnoses. Wild tomatoes, members ofSolanumsect.Lycopersicum, are commonly used as a source of exotic germplasm for improvement of the cultivated tomato, and are increasingly employed in basic research. Although the section experienced significant early work, which continues presently, the taxonomic status of many wild species has undergone a number of significant revisions and remains uncertain. Species in this section vary in their breeding systems, notably the expression of self‐incompatibility, which determines individual propensity for outcrossing

Here, we examine the taxonomic status of obligately outcrossing Chilean wild tomato (Solanum chilense) using reduced‐representation sequencing (RAD‐seq), a range of phylogenetic and population genetic analyses, as well as analyses of crossing and morphological data.

Overall, each of our analyses provides a considerable weight of evidence that the Pacific coastal populations and Andean inland populations of the currently describedSolanum chilenserepresent separately evolving populations, and conceal at least one undescribed cryptic species.

Despite its vast economic importance,Solanumsect.Lycopersiconstill exhibits considerable taxonomic instability. A pattern of under‐recognition of outcrossing species may be common, not only in tomatoes, but across flowering plants. We discuss the possible causes and implications of this observation, with a focus on macroevolutionary inference.