Hybridization may facilitate in situ survival of endemic species through periods of climate change

Abstract

Predicting survival and extinction scenarios for climate change requires an understanding of the present day ecological characteristics of species and future available habitats, but also the adaptive potential of species to cope with environmental change. Hybridization is one mechanism that could facilitate this. Here we report statistical evidence that the transfer of genetic information through hybridization is a feature of species from the plant genus Pachycladon that survived the Last Glacial Maximum in geographically separated alpine refugia in New Zealand's South Island. We show that transferred glucosinolate hydrolysis genes also exhibit evidence of intralocus recombination. Such gene exchange and recombination has the potential to alter the chemical defence in the offspring of hybridizing species. We use a mathematical model to show that when hybridization increases the adaptive potential of species, future biodiversity will be best protected by preserving closely related species that hybridize rather than by conserving distantly related species that are genetically isolated. Predicting the response of organisms and estimating loss of genetic diversity are important challenges for evaluating the impact of global climate change on biodiversity 1-3. Although ecological modelling has an important place in understanding this impact 2 , an accurate prediction of range shift and extinction of species also requires determining their adaptive potential, and in particular the frequency with which hybridization facilitates adaptation 4. Determining this is important, because although hybridization can be a maladaptive phenomenon 5 , it might also help species to acquire adaptive traits, respond successfully to environmental change and invade new habitats 1,3,4,6-8. A better understanding of its positive and negative contributions is essential for evaluating biodiversity impacts. Species affected by climate change in the past-the consequences of which are manifested in extant species' ranges and patterns of genetic diversity-provide models to test for signatures of hybridization. Here we studied Pachycladon (Brassicaceae), an allopolyploid genus of 11 species 9 that have radiated in the New Zealand Alps during the Pleistocene period 9,10. Figure 1 shows ice cover at the height of the Last Glacial Maximum (LGM; 21,000-18,000 years ago), the present day distribution of three Pachycladon species, and a chloroplast TCS (statistical parsimony) haplotype network indicating relationships among accessions of the three species. At present, all three species are restricted to greywacke rock in the central and northern regions of the South Island of New

Interspecific Hybridization May Provide Novel Opportunities for Coral Reef Restoration

“…The results provide evidence that hybridization may have value to reef restoration. From the restoration point of view, hybridization increases genetic variation which can potentially enhance adaptive capacity and release a population from adaptive limits Becker et al, 2013;Carlson et al, 2014;van Oppen et al, 2015;Hamilton and Miller, 2016;Meier et al, 2017). In this study, genetic diversity would have increased in the F1 hybrids and positive effects on survival and recruits size were observed in some cases.…”

“…However, anthropogenic disturbances are rapidly changing the environment and shifting selection pressures (Becker et al, 2013), and locally sourced stock is therefore potentially mismatched with the altered environment. An effective restoration strategy should thus incorporate an understanding of present day ecological characteristics of species, characteristics of future available habitats, and adaptive potential of species (Becker et al, 2013). The use of non-local and climate resilient materials is controversial, but is gaining traction in wildland restoration (Jones and Monaco, 2009), revegetation Breed et al, 2013), and coral reef restoration (Rau et al, 2012;van Oppen et al, 2017).…”

“…Traditionally, locally sourced biological material is used for restoration based on the assumption that these populations are locally adapted and therefore most likely to survive (Breed et al, 2013). However, anthropogenic disturbances are rapidly changing the environment and shifting selection pressures (Becker et al, 2013), and locally sourced stock is therefore potentially mismatched with the altered environment. An effective restoration strategy should thus incorporate an understanding of present day ecological characteristics of species, characteristics of future available habitats, and adaptive potential of species (Becker et al, 2013).…”

“…The value of hybridization in enhancing fitness has been demonstrated in multiple cases. For instance, hybridization has provided genetic variance in morphology for adapting to changing environments in Darwin's finches (Grant and Grant, 2010), altered chemical defense of hybrid Brassicaceae plants and aided their survival through the Last Glacial Maximum (Becker et al, 2013), and facilitated extensive adaptive radiation in haplochromine cichlid fishes (Meier et al, 2017).…”

“…One possible way to improve the adaptive potential of species is via hybridization, which can increase genetic variation, break genetic correlations that constrain evolvability of parental lineages, and assist species to acquire adaptive traits Becker et al, 2013;Carlson et al, 2014;van Oppen et al, 2015;Hamilton and Miller, 2016;Meier et al, 2017). Hybridization can be conducted either via targeted crossing of individuals or species carrying desired phenotypic traits (e.g., high thermal tolerance) or via crossing between species with the goal of increasing genetic diversity and new variation for natural selection to act upon, and potentially generating hybrid 1 https://50reefs.org/ (Accessed April 3, 2018).…”