Untitled

Funder

Organizational Unit

Publications

Genes left behind: Climate change threatens cryptic genetic diversity in the canopy-forming seaweed bifurcaria bifurcata

Publication . Neiva, J.; Assis, J.; Coelho, Nelson; Fernandes, Francisco; Pearson, Gareth; Serrao, Ester A.

The global redistribution of biodiversity will intensify in the coming decades of climate change, making projections of species range shifts and of associated genetic losses important components of conservation planning. Highly-structured marine species, notably brown seaweeds, often harbor unique genetic variation at warmer low-latitude rear edges and thus are of particular concern. Here, a combination of Ecological Niche Models (ENMs) and molecular data is used to forecast the potential near-future impacts of climate change for a warm-temperate, canopy forming seaweed, Bifurcaria bifurcata. ENMs for B. bifurcata were developed using marine and terrestrial climatic variables, and its range projected for 2040-50 and 2090-2100 under two greenhouse emission scenarios. Geographical patterns of genetic diversity were assessed by screening 18 populations spawning the entire distribution for two organelle genes and 6 microsatellite markers. The southern limit of B. bifurcata was predicted to shift northwards to central Morocco by the mid-century. By 2090-2100, depending on the emission scenario, it could either retreat further north to western Iberia or be relocated back to Western Sahara. At the opposing margin, B. bifurcata was predicted to expand its range to Scotland or even Norway. Microsatellite diversity and endemism were highest in Morocco, where a unique and very restricted lineage was also identified. Our results imply that B. bifurcata will maintain a relatively broad latitudinal distribution. Although its persistence is not threatened, the predicted extirpation of a unique southern lineage or even the entire Moroccan diversity hotspot will erase a rich evolutionary legacy and shrink global diversity to current (low) European levels. NW Africa and similarly understudied southern regions should receive added attention if expected range changes and diversity loss of warm-temperate species is not to occur unnoticed.

2015-07Journal article

Open Access

Role of spawning synchrony on hybridization barriers in sympatric intertidal fucoid algae - when and why

Publication . Monteiro, Carla Alexandra da Silva; Pearson, Gareth; Serrão, Ester; Valero, Myriam

In sympatric assemblages of congeners with incomplete reproductive barriers, the synchrony within species and asynchrony between species may be under strong selection, reinforcing prezygotic reproductive isolation and reducing hybridization. Interspecific asynchrony and gametic incompatibility are considered the two most important prezygotic mechanisms reinforcing assortative mating and acting against hybridization. However, divergence of reproductive strategies in closely related species might also contribute to reproductive isolation. The main goal of this thesis was to investigate hypotheses concerning the mechanisms that act against hybridization in sympatric species with external fertilization, including the asynchrony of gamete release, mating system variations and gametic incompatibility. As a model we used sympatric Fucus species with different reproductive modes, hermaphroditic (selfing) and dioecious (obligate outcrossing). The results show a clear relationship between patterns of gamete release and tidal/circadian cycles that contributes to interspecific variation in spawning time between hermaphroditic and dioecious species. The data support the hypothesis that asynchronous egg release acts as a prezygotic barrier to hybridization between hermaphroditic and dioecious species, and therefore, that mating system variation between congeners plays important role against hybridization. We also provide evidence that gametic incompatibility is an incomplete prezygotic barrier between Fucus species. Results show the potential of interspecific fertilization, and the potential growth and survival of hybrids relative to the parental lineage.

2016-07-07Doctoral thesis

Open Access

Shift happens: trailing edge contraction associated with recent warming trends threatens a distinct genetic lineage in the marine macroalga Fucus vesiculosus

Publication . Nicastro, Katy R; I Zardi, Gerardo; Teixeira, Sara; Neiva, J.; Serrão, Ester; Pearson, G. A.

Significant effects of recent global climate change have already been observed in a variety of ecosystems, with evidence for shifts in species ranges, but rarely have such consequences been related to the changes in the species genetic pool. The stretch of Atlantic coast between North Africa and North Iberia is ideal for studying the relationship between species distribution and climate change as it includes the distributional limits of a considerable number of both cold- and warm-water species. We compared temporal changes in distribution of the canopy-forming alga Fucus vesiculosus with historical sea surface temperature (SST) patterns to draw links between range shifts and contemporary climate change. Moreover, we genetically characterized with microsatellite markers previously sampled extinct and extant populations in order to estimate resulting cryptic genetic erosion. Results Over the past 30 years, a geographic contraction of the southern range edge of this species has occurred, with a northward latitudinal shift of approximately 1,250 km. Additionally, a more restricted distributional decline was recorded in the Bay of Biscay. Coastal SST warming data over the last three decades revealed a significant increase in temperature along most of the studied coastline, averaging 0.214°C/decade. Importantly, the analysis of existing and extinct population samples clearly distinguished two genetically different groups, a northern and a southern clade. Because of the range contraction, the southern group is currently represented by very few extant populations. This southern edge range shift is thus causing the loss of a distinct component of the species genetic background. Conclusions We reveal a climate-correlated diversity loss below the species level, a process that could render the species more vulnerable to future environmental changes and affect its evolutionary potential. This is a remarkable case of genetic uniqueness of a vanishing cryptic genetic clade (southern clade).

2013-01-23Journal article

Open Access

Population dynamics of temperate kelp forests near their low-latitude limit

Publication . Pereira, Tânia R.; Engelen, Aschwin; Pearson, Gareth; Valero, Myriam; Serrao, Ester

Climate change tends to shift species ranges polewards. Demographic processes at the rear edge are particularly interesting yet poorly understood. This study aimed to provide insights in population dynamics and resilience of temperate kelp populations at their shallower and lower latitude distribution limits, in northern Portugal. Intertidal populations of the perennial Laminaria ochroleuca, Laminaria hyperborea and the annual Saccorhiza polyschides were censused for two years and projection matrix models used to assess their demographic state and the most important demographic processes for their maintenance and growth. Furthermore, during the second year of census, the northern Portuguese coast was impacted by a late winter storm that caused extensive damage to these communities, allowing an assessment of their resilience. Yearly climate variations may affect the recruitment timing of S. polyschides, preventing sporophytes from reaching maturity, thus impairing spore production, rendering the population entirely dependent on the survival of microscopic forms. Year-round spore production by L. ochroleuca is advantageous, as it is less likely impaired by occasional extreme events. Still, while recovery of L ochroleuca took longer than two years. S. polyschides, was able to recover the following year. If future recurrence and duration of such highly energetic storms increases with climate change; these populations are expected to become gradually younger, providing less canopy. In contrast, no recovery of L hyperborea was observed. Lack of reproductive success, limited dispersal from neighboring populations and abiotic factors might have contributed to the impaired repopulation. Species persistence follows its strategy, with opportunistic species revealing higher resilience. (C) 2017 Elsevier B.V. All rights reserved.

2017-03Journal article

Restricted

Fine-scale genetic breaks driven by historical rangedynamics and ongoing density-barrier effects in theestuarine seaweed Fucus ceranoides L.

Publication . Neiva, J.; Pearson, G. A.; Valero, Myriam; Serrão, Ester

Factors promoting the emergence of sharp phylogeographic breaks include restricted dispersal, habitat discontinuity, physical barriers, disruptive selection, mating incompatibility, genetic surfing and secondary contact. Disentangling the role of each in any particular system can be difficult, especially when species are evenly distributed across transition zones and dispersal barriers are not evident. The estuarine seaweed Fucus ceranoides provides a good example of highly differentiated populations along its most persistent distributional range at the present rear edge of the species distribution, in NW Iberia. Intrinsic dispersal restrictions are obvious in this species, but have not prevented F. ceranoides from vastly expanding its range northwards following the last glaciation, implying that additional factors are responsible for the lack of connectivity between neighbouring southern populations. In this study we analyze 22 consecutive populations of F. ceranoides along NW Iberia to investigate the processes generating and maintaining the observed high levels of regional genetic divergence. Results Variation at seven microsatellite loci and at mtDNA spacer sequences was concordant in revealing that Iberian F. ceranoides is composed of three divergent genetic clusters displaying nearly disjunct geographical distributions. Structure and AFC analyses detected two populations with an admixed nuclear background. Haplotypic diversity was high in the W sector and very low in the N sector. Within each genetic cluster, population structure was also pervasive, although shallower. Conclusions The deep divergence between sectors coupled with the lack of support for a role of oceanographic barriers in defining the location of breaks suggested 1) that the parapatric genetic sectors result from the regional reassembly of formerly vicariant sub-populations, and 2) that the genetic discontinuities at secondary contact zones (and elsewhere) are maintained despite normal migration rates. We conclude that colonization and immigration, as sources of gene-flow, have very different genetic effects. Migration between established populations is effectively too low to prevent their differentiation by drift or to smooth historical differences inherited from the colonization process. F. ceranoides, but possibly low-dispersal species in general, appear to be unified to a large extent by historical, non-equilibrium processes of extinction and colonization, rather than by contemporary patterns of gene flow.

2012-06-06Journal article

Open Access