Species assemblage networks identify regional connectivity pathways among hydrothermal vents in the Northwest Pacific

Abstract

The distribution of species among spatially isolated habitat patches supports regional biodiversity and stability, so understanding the underlying processes and structure is a key target of conservation. Although multivariate statistics can infer the connectivity processes driving species distribution, such as dispersal and habitat suitability, they rarely explore the structure. Methods from graph theory, applied to distribution data, give insights into both connectivity pathways and processes by intuitively formatting the data as a network of habitat patches. We apply these methods to empirical data from the hydrothermal vent habitats of the Northwest Pacific. Hydrothermal vents are “oases” of biological productivity and endemicity on the seafloor that are imminently threatened by anthropogenic disturbances with unknown consequences to biodiversity. Here, we describe the structure of species assemblage networks at hydrothermal vents, how local and regional parameters affect their structure, and the implications for conservation. Two complementary networks were formed from an extensive species assemblage dataset: a similarity network of vent site nodes linked by weighted edges based on their pairwise assemblage similarity and a bipartite network of species nodes linked to vent site nodes at which they are present. Using these networks, we assessed the role of individual vent sites in maintaining network connectivity and identified biogeographic sub‐regions. The three sub‐regions and two outlying sites are separated by their spatial arrangement and local environmental filters. Both networks detected vent sites that play a disproportionately important role in regional pathways, while the bipartite network also identified key vent sites maintaining the distinct species assemblages of their sub‐regions. These regional connectivity pathways provide insights into historical colonization routes, while sub‐regional connectivity pathways are of value when selecting sites for conservation and/or estimating the multivent impacts from proposed deep‐sea mining.

Hydrothermal vent fauna of the western Pacific Ocean: Distribution patterns and biogeographic networks

“…We use methods from graph theory to formulate a similarity network of nodes connected by edges as applied to extant vent assemblages by Brunner et al. (2022). In our work, nodes are vent systems and edges represent undirected relationships based in faunal similarity.…”

“…We use a combination of methods to assess patterns of diversity distribution and potential connections across the study area based on these records. This approach follows two recent studies: (i) Brunner et al (2022)…”

“…This approach follows two recent studies: (i) Brunner et al. (2022) apply two complementary methods from graph theory to examine connections among 36 vent sites in the Northwest Pacific and identify priority sites for conservation, and (ii) Giguère and Tunnicliffe (2021) examine the Mariana region of the Northwest Pacific to explore β ‐diversity patterns among vent sites. Our work supplements the data in these two studies with recent Northwest Pacific vent species reports and expands from these four vent systems to encompass an additional seven systems in the Southwest Pacific.…”

The Role of Reproductive Periodicity in Dispersal Among Hydrothermal Vents and its Implications for Regional Connectivity and Conservation

“…The geographical extent of these simulations is limited to an area of the Northwest Pacific which represents a distinct bioregion (Bachraty et al 2009) with little influence from dispersal from external sites (Mitarai et al ., 2016). Local and regional diversity is particularly high in the Northwest Pacific compared to other hydrothermal vent regions (Thaler and Amon, 2019) and species distributions are somewhat spatially structured (Brunner et al ., 2022) within the region. This region is also home to the world’s first full-scale test mining of a hydrothermal vent ecosystem, which was carried out in the central Okinawa Trough in 2017 (Okamoto et al ., 2019).…”

Genetic divergence and migration patterns of a galatheoid squat lobster highlight the need for deep‐sea conservation

“…Consequently, there has been an increasing urgency in studying the population connectivity of vent‐ and/or seep‐dwelling species, especially their genetic divergence and migration patterns. Such knowledge could cast light on the biogeographical subdivisions and source‐sink dynamics of specialist species, and provide scientific guidelines for the management of deep‐sea biodiversity confronted with local anthropogenic disturbances and global climate change (Baco et al., 2016; Brunner et al., 2022). Nevertheless, related studies are still scarce, which greatly hinders the data‐driven planning of deep‐sea conservation.…”