The first global macrogenetic map of marine habitat-forming species

Newswise — Organisms such as gorgonians, corals, algae, seaweeds, and marine phanerogams are vital in shaping underwater landscapes and serving as habitats. They act as natural shelters for other species, contributing to the biomass and complexity of the seabed. However, these crucial marine species are currently under threat from climate change and human-induced disturbances. A recent publication in the journal Global Ecology and Biogeography cautions that even within marine protected areas (MPAs), the safeguarding of genetic diversity in structural species is inadequate. This genetic diversity is essential for populations to respond and adapt to environmental changes that disrupt the natural equilibrium.

Laura Figuerola-Ferrando, Cristina Linares, Ignasi Montero-Serra, and Marta Pagès-Escolà, affiliated with the Faculty of Biology at the University of Barcelona and the Biodiversity Research Institute of the UB (IRBio), conducted the study. Jean-Baptiste Ledoux and Aldo Barreiro, from the Interdisciplinary Centre of Marine and Environmental Research (CIIMAR) in Portugal, as well as Joaquim Garrabou, from the Institute of Marine Sciences (ICM-CSIC), were also involved in the research.

Genetic diversity is also a component of biodiversity

Historically, management and conservation plans for marine biodiversity have predominantly focused on factors such as species richness. However, genetic diversity, which represents the variation in genetic characteristics within a species, is another significant aspect of biodiversity. It plays a crucial role in determining the adaptive capacity and long-term survival of populations. Regrettably, genetic diversity has often been neglected in existing management and conservation strategies.

Laurz Figuerola-Ferrando, the lead researcher and first author of the study, emphasizes that genetic diversity plays a critical role in bolstering the capacity of species, populations, and communities to effectively adapt to swift environmental changes caused by climate change. By enhancing genetic diversity, these entities can enhance their resilience and improve their chances of withstanding and responding to the challenges posed by a changing climate.

"However," she continues, "up until now, the predominant approach in establishing marine protected areas has focused on the presence of various species and habitats, without taking into account their genetic diversity. Similarly, the red list of the International Union for Conservation of Nature (IUCN) also fails to incorporate genetic diversity as a criterion."

"In recent years, there has been a growing recognition of the importance of prioritizing the protection of genetic diversity in conservation efforts," states the researcher from the Department of Evolutionary Biology, Ecology, and Environmental Sciences of the UB. They further highlight that advancements in technology, enabling the widespread use of various techniques to assess genetic diversity (such as microsatellites or analysis of small DNA fragments), have made it more feasible and cost-effective to incorporate genetic diversity considerations into management and conservation plans.

From the northwest Atlantic to the Gulf of Guinea

The study utilizes macrogenetic techniques to examine broad genetic patterns across a range of marine species on a large spatial scale. The authors have conducted an analysis using data sourced from a global database. This database encompasses genetic diversity information, specifically derived from microsatellites, for over 9,300 populations of 140 species across various marine regions worldwide.

The findings of the study provide a comprehensive overview of genetic patterns observed in marine habitat-forming species, including corals, macroalgae, marine phanerogams, and others. These genetic patterns serve as a reference scenario that can be valuable in enhancing the effectiveness of management and conservation plans for marine life. By considering these genetic patterns, decision-makers and conservationists can make more informed choices to ensure the preservation and sustainable management of marine habitats.

The study reveals that the regions with the highest levels of genetic diversity in marine landscape species are the northwest Atlantic provinces and the Bay of Bengal. These regions exhibit notably high values of genetic diversity, surpassing the global average. Additionally, the Mediterranean region has also been identified as having relatively high levels of genetic diversity. On the other hand, the marine provinces with the lowest values of genetic diversity are the Gulf of Guinea and the southwest Atlantic.

The study's results further highlight a positive correlation between genetic diversity and species richness among animal and plant marine habitat-forming species. This correlation underscores the importance of considering genetic diversity in conjunction with species richness for effective conservation efforts. However, the paper issues a concerning warning that the Network of Marine Protected Areas (RAMP) in large oceanic ecoregions does not adequately safeguard areas with the highest genetic diversity of marine habitat-forming species. This indicates a significant gap in current conservation measures and emphasizes the need for improved protection strategies that prioritize genetic diversity.

Laura Figuerola-Ferrando, who is currently working on her doctoral thesis under the supervision of Cristina Linares (UB) and Joaquim Garrabou (ICM-CSIC), highlights an important observation. The study's initial hypothesis presumed that marine protected areas (MPAs) would exhibit greater genetic diversity compared to areas outside of them. However, the research findings reveal that this is not the case. Surprisingly, there are no significant differences in genetic diversity between inside and outside the MPAs on a global scale. This indicates a critical gap in the protection of genetic diversity within MPAs, a concerning finding that calls for urgent attention in conservation efforts.

A new pattern of equatorial biodiversity at the poles

In addition to the earlier findings, the authors of the study have identified a distinctive distribution pattern of genetic diversity among marine habitat-forming species. This pattern deviates from the traditional models known thus far. The observed pattern follows a bimodal latitudinal distribution, revealing a complex biogeographic model. According to Cristina Linares (UB-IRBio), an ICREA Academia professor and one of the study's coordinators, the bimodal pattern indicates that the genetic diversity of these species exhibits two peaks in temperate zones, with a slight dip in genetic diversity at the equator. This finding adds to our understanding of the global distribution of genetic diversity in marine habitat-forming species. The study was coordinated by Cristina Linares (UB-IRBio) and Jean-Baptiste Ledoux (CIIMAR).

This scientific discovery holds significant relevance because it challenges the long-held belief that the distribution of biodiversity on our planet follows a unimodal pattern, with maximum values at the equator and decreasing towards the poles. Particularly in marine ecosystems, this traditional understanding does not always hold true. As Cristina Linares explains, the pattern observed in benthic species, both in terms of species richness and genetic diversity, is actually bimodal rather than unimodal. This means that there are two peaks in biodiversity, not just one, with higher values found in temperate zones. This insight highlights the complexity and unique characteristics of biodiversity distribution in marine ecosystems, providing a more nuanced understanding of how genetic diversity is distributed across different latitudes.

Jean-Baptiste Ledoux, a researcher from CIIMAR, adds valuable insights to the study's findings. He highlights that the bimodal latitudinal pattern observed in the distribution of genetic diversity is influenced by taxonomy. Specifically, the study reveals statistically significant differences between animal species, which exhibit higher genetic diversity, and plant species, which display lower genetic diversity. Moreover, when examining the latitudinal pattern separately for animals and plants, the bimodal pattern persists in animals, but not in plants. This suggests that the factors influencing genetic diversity and its distribution may vary between different taxonomic groups, highlighting the importance of considering taxonomic distinctions in understanding the patterns observed.

Genetic diversity: improving conservation management plans

The conclusions of the study highlight the critical importance of integrating population genetic diversity into biodiversity management and conservation plans worldwide. Jean-Baptiste Ledoux points out that the significance of genetic diversity in such plans has recently been emphasized through the "Kunming-Montreal Global Biodiversity Framework" under the Convention on Biological Diversity (CBD/COP/15/L25, 2022). In light of this context, the study's establishment of a baseline for genetic diversity patterns in marine habitat-forming species becomes particularly relevant. The findings of the study can provide valuable insights and inform conservation strategies aimed at preserving and managing genetic diversity in marine ecosystems, aligning with the objectives outlined in the global biodiversity framework.

Additionally, the study highlights the prominence of the Mediterranean and Atlantic regions in the scientific literature concerning macrogenetic patterns of deep-sea structural species. These regions are extensively represented in the literature utilized for this study, underscoring their significant contributions to our understanding of genetic patterns in these species.

The researchers conclude that when considering the analyzed taxa, the Mediterranean Sea stands out as the marine province with the most extensive range of studies across various taxa, including octocorals, hexacorals, sponges, marine phanerogams, and algae. In the northern Atlantic, there is also a considerable diversity of taxa investigated, primarily algae and marine phanerogams, but also including hexacorals, octocorals, bryozoans, and sponges. Conversely, studies conducted in the southern Atlantic predominantly focus on algae. This highlights the varying taxonomic focus across different regions, with the Mediterranean Sea and northern Atlantic showcasing a broader range of taxa examined compared to the southern Atlantic.