The role of time and species identities in spatial patterns of species richness and conservation

Abstract

Many conservation actions are justified on the basis of managing biodiversity. Biodiversity, in terms of species richness, is largely the product of rare species. This is problematic because the intensity of sampling needed to characterize communities and patterns of rarity or to justify the use of surrogates has biased sampling in favor of space over time. However, environmental fluctuations interacting with community dynamics lead to temporal variations in where and when species occur, potentially affecting conservation planning by generating uncertainty about results of species distribution modeling (including range determinations), selection of surrogates for biodiversity, and the proportion of biodiversity composed of rare species. To have confidence in the evidence base for conservation actions, one must consider whether temporal replication is necessary to produce broad inferences. Using approximately 20 years of macrofaunal data from tidal flats in 2 harbors, we explored variation in the identity of rare, common, restricted range, and widespread species over time and space. Over time, rare taxa were more likely to increase in abundance or occurrence than to remain rare or disappear and to exhibit temporal patterns in their occurrence. Space-time congruency in ranges (i.e., spatially widespread taxa were also temporally widespread) was observed only where samples were collected across an environmental gradient. Fifteen percent of the taxa in both harbors changed over time from having spatially restricted ranges to having widespread ranges. Our findings suggest that rare species can provide stability against environmental change, because the majority of species were not random transients, but that selection of biodiversity surrogates requires temporal validation. Rarity needs to be considered both spatially and temporally, as species that occur randomly over time are likely to play a different role in ecosystem functioning than those exhibiting temporal structure (e.g., seasonality). Moreover, temporal structure offers the opportunity to place management and conservation activities within windows of maximum opportunity.

Long-term (1998 vs. 2010) large-scale comparison of soft-bottom benthic macrofauna composition in the Gulf of Lions, NW Mediterranean Sea

“…The composition of benthic macrofauna may, however, vary with time and even the identity of dominant species may change from one year to the other in response to climatic variations. Such changes have been reported by several authors around the world such as in Brazil (Bernadino et al, 2015), in New Zealand (Hewitt et al, 2016), in southwest England (Mieszkowska et al, 2014), in the southern North Sea (Kröncke et al, 1998(Kröncke et al, , 2001(Kröncke et al, , 2011, in western Sweden (Tunberg and Nelson, 1998;Hagberg and Tunberg, 2000) or in the Mediterranean Sea (Grémare et al, 1998a;Salen-Picard et al, 2002;Labrune et al, 2007b). These studies show a direct or indirect effect of climatic variations on macrofauna communities.…”

Freshwater eutrophication drives sharp reductions in temporal beta diversity

“…, Hewitt et al. ). Incorporating appropriate temporal extent into study design is vital to address ecological questions that may be influenced by temporal factors, and the majority of studies to date have either focused on a temporal scale too fine to detect seasonality (~1 month duration; Brown ), or on a temporal extent aimed at assessing long‐term community stability (repeated sampling of the same time point over multiple years; Mykrä et al.…”

Enhanced biodiversity and abundance of benthic invertebrate macrofauna in a New Zealand marine reserve

“…from bottom fishing) (Sciberras et al, 2013), a non‐extractive marine reserve where pressure from bottom‐fishing practices is removed is likely to be the most powerful tool for protecting the complex benthic habitat and the invertebrates that use this landscape. Complex variable benthic landscapes can host more diverse fauna (Dumas et al, 2013; Thrush et al, 2001), and habitat heterogeneity within Paterson Inlet/Whaka a Te Wera may be responsible for the high biodiversity through the availability of many potential niches (Collier et al, 2016; Hewitt, Thrush, & Ellingsen, 2016).…”