Evolution and conservation genetics of an insular hemiparasitic plant lineage at the limit of survival: the case of Thesium sect. Kunkeliella in the Canary Islands.

PREMISE: The diversification of island flora has been widely studied. However, the role of environmental niches in insular radiation processes has been less investigated. We combined population genetic analyses with species distribution modelling to clarify the genetic relationships, diversification patterns, species niche requirements, and conservation of Thesium sect. Kunkeliella, a clade of rare hemiparasitic plants endemic to the Canaries. METHODS: We studied the three extant Thesium species and a new taxon from La Palma Island. We developed 12 microsatellites and performed population genetic analysis and studied the demographic history of the group. To evaluate the role of niche conservatism in the diversification of the group, we performed species distribution modelling (ESM) with four algorithms. RESULTS: All species presented moderate genetic diversity values for rare endemics. Thesium canariense (Gran Canaria) showed high differentiation, whereas T. subsucculentum, T. retamoides (Tenerife), and La Palma populations are closely related. The lineage may have undergone a recent diversification with colonization proceeding east to west, with T. canariense as sister to the others. We detected a climatic niche shift, as taxa showed different distributions across the temperature gradient. There is enough evidence to describe La Palma populations as a new species. CONCLUSIONS: We characterized the evolutionary history of Thesium sect. Kunkeliella by integrating genetic and ecological assessments. Our results indicate that this clade has undergone a recent radiation process with niche differentiation among species. The results increase our knowledge about insular radiations and will inform the conservation management of the study species.

The restoration of the endangered Sambucus palmensis after 30 years of conservation actions in the Garajonay National Park: genetic assessment and niche modeling.

The translocation of individuals or the reinforcement of populations are measures in the genetic rescue of endangered species. Although it can be controversial to decide which and how many individuals must be reintroduced, populations can benefit from reinforcements. Sambucus palmensis is a critically endangered endemic to the Canary Islands. During the past 30 years, the Garajonay National Park (La Gomera) has carried out an intensive program of translocations using cuttings, due to the low germination rates of seeds. To assess the effect of the restorations on the population genetics of S. palmensis in La Gomera, we collected 402 samples from all the restored sites and all known natural individuals, which were genotyped with seven microsatellite markers. In addition, we conducted a species distribution modeling approach to assess how restorations fit the ecological niche of the species. Results show that there is a high proportion of clone specimens due to the propagation method, and the natural clonal reproduction of the species. Nonetheless, the observed heterozygosity has increased with the restorations and there still are private alleles and unique genotypes in the natural populations that have not been considered in the restorations. The population of Liria constitutes a very important genetic reservoir for the species. To optimize future reintroductions, we have proposed a list of specimens that are suitable for the extraction of seeds or cuttings in a greenhouse, as well as new suitable areas obtained by the species distribution models.

Ornithophily for the nonspecialist: Differential pollination efficiency of the Macaronesian island paleoendemic Navaea phoenicea (Malvaceae) by generalist passerines.

PREMISE OF THE STUDY: A bird pollination syndrome exists in the Canary Islands archipelago across independent plant lineages despite the absence of specialist birds. The pollination efficiency of current floral visitors remains unknown for many plant species despite this being a fundamental factor in testing hypotheses about the origin of the syndrome. Here, we studied the components of pollination efficiency in the paleoendemic Navaea phoenicea, a species exhibiting conspicuous anatomical modifications associated with bird pollination. METHODS: We measured the components of the pollination efficiency (PE) of species foraging on flowers. The measured quantitative components were visitation frequency patterns to plants and individual flowers. The qualitative components were the contributions to the fitness of male and female functions (pollen removal and deposition and fruit set). KEY RESULTS: Pollination by warbler species was highly efficient, but visit frequency was low; conversely, Canarian chiffchaffs had high visit frequency and low efficiency. Overall PE was almost 0 for blue tits due to disruptive behavior. We also found insects acting as nectar robbers. CONCLUSIONS: Pollination efficiency of three of the four bird species visiting flowers of Navaea phoenicea may be high enough to maintain selective pressure on floral traits of a relict pollination syndrome. The behavior of these birds plays a crucial role in their pollination efficiency. Perching, by generalist passerines when visiting N. phoenicea flowers, is the most efficient habit. The frequency and PE of insect visits calls into question their role as legitimate visitors.

Pollinator shifts drive petal epidermal evolution on the Macaronesian Islands bird-flowered species.

Pollinator shifts are considered to drive floral trait evolution, yet little is still known about the modifications of petal epidermal surface at a biogeographic region scale. Here we investigated how independent shifts from insects to passerine birds in the Macaronesian Islands consistently modified this floral trait (i.e. absence of papillate cells). Using current phylogenies and extensive evidence from field observations, we selected a total of 81 plant species and subspecies for petal microscopy and comparative analysis, including 19 of the 23 insular species pollinated by opportunistic passerine birds (Macaronesian bird-flowered element). Species relying on passerine birds as the most effective pollinators (bird-pollinated) independently evolved at least five times and in all instances associated with a loss of papillate cells, whereas species with a mixed pollination system (birds plus insects and/or other vertebrates) evolved at least five times in Macaronesia and papillate cells were lost in only 25% of these transitions. Our findings suggest that petal micromorphology is a labile trait during pollinator shifts and that papillate cells tend to be absent on those species where pollinators have limited mechanical interaction with flowers, including opportunistic passerine birds that forage by hovering or from the ground.