Plant conservation in a changing world: modelling range dynamics, climate adaptation, and effects of habitat fragmentation

Climate change can alter the physical and biological parameters of existing habitats, shifting environmental variables beyond the range for which native plant species are adapted. These changes compel plant species to either adapt to new conditions or migrate to areas where conditions remain suitable. Concurrently, habitat fragmentation reduces the amount of suitable habitat and impedes plant species' ability to migrate, thereby reducing the genetic diversity within isolated populations. These stressors interact to amplify each other's impacts, thereby escalating the vulnerabilities of plant species. The accelerated pace of climate change often exceeds both the capacity for plant species to adapt or migrate, leaving them vulnerable to decline or extinction.

In a rapidly changing world, effective plant conservation hinges on a nuanced understanding of how species interact with, adapt to, and persist within their environments. To safeguard plant species facing concurrent environmental stressors, there's a pressing need to develop integrated tools that can accurately forecast their eco-evolutionary responses to climate adaptation and habitat fragmentation. Utilising an interdisciplinary approach that includes species distribution modelling, conservation genomics, and experimental ecology, this study has developed complementary models that serve as a critical foundation for devising dynamic and resilient conservation strategies.

To develop integrated conservation tools that enable effective implementation of proactive mitigation strategies, Primula elatior was chosen as a representative model species for plants that have high habitat fidelity, display climate sensitivity, and are sensitive to habitat fragmentation. Its geographical distribution along the Atlantic Biogeographic Region facilitates the study of local adaptation to varying climate conditions. The species is notably vulnerable to drought, providing a unique perspective for evaluating the effects of climate change on plant survival and reproduction. Additionally, P. elatior exhibits a herkogamous, self-incompatible mating system, making it an ideal candidate for investigating how mating systems are influenced by eco-evolutionary feedback loops in fragmented habitats. Its limited seed dispersal and constrained colonisation aptly reflect the challenges faced by many European forest herbs, thereby offering broader ecological insights. Moreover, the species' distylous flowers and bee-dependent pollination present a case study for the sensitivity to Allee-effects commonly found in self-incompatible European forest herbs, further solidifying its value as a model for studying the intertwined ecological and evolutionary consequences of habitat fragmentation.

First, to evaluate the fundamental niche, a high-resolution species distribution model was developed using landscape and macro-climatic variables in order to model the range-wide habitat suitability for P. elatior. Second, to evaluate the accessible niche, a fine-grained genetically optimised dispersal model was developed to simulate spatio- temporal dispersal patterns among habitat patches. Third, in our quest to evaluate population persistence, a proximity resistance index was calculated to predict the meta-population stability. By simulating spatio-temporal patterns in the accessible niche and meta-population stability, we could identify habitat-specific conservation and mitigation strategies for ecological restoration. Next, through the integration of genetically optimised dispersal models with state-of-the-art landscape genomics, it became possible to predict climate sensitivity, a crucial metric encapsulating both genomic offset and adaptive potential. Furthermore, landscape ecological methods were employed to evaluate the impact of habitat fragmentation on the adaptive genomic architecture of P. elatior. Lastly, to evaluate the impact of varying environmental conditions on plant adaptive responses, a common garden experiment was conducted. This experiment involved P. elatior progeny from populations along a climate cline and varying levels of habitat fragmentation, enabling a comprehensive assessment of local adaptation and phenotypic plasticity.

The eco-evolutionary dynamics of climate adaptation and habitat fragmentation compound to jeopardise the accessible distribution range and meta-population stability of P. elatior. The species faces severe limitations in its ability to naturally migrate to new favourable habitats, severely affecting species persistence. Moreover, our genomic analyses caution against relying solely on assisted migration strategies, particularly from southern source populations, due to their low adaptive capacities and risk of non-climatic maladaptation. These multi-layered challenges not only impede natural dispersal but also diminish the species' evolutionary capacity to adapt to changing climatic conditions. Furthermore, habitat fragmentation disrupts established climate clines of several traits, hampers drought tolerance, and alters mating system adaptations, as evidenced by the common garden experiment and field survey of herkogamy. These eco-evolutionary consequences highlight the necessity for integrated conservation approaches that are both multi-faceted and regionally tailored, encompassing habitat restoration, carefully planned assisted migration, and continuous monitoring of genetic diversity and adaptability.