Geographic variation in species richness, rarity, and the selection of areas for conservation: An integrative approach with Brazilian estuarine fishes
Introduction
Spatial conservation strategies are often based on geographic patterns of biodiversity (Roberts et al., 2002, Brooks et al., 2006). To be effective, such strategies require spatially accurate and representative information on the distribution of biota. The lack of detailed data on geographic distribution of most biological groups, however, has not only hindered the application of methods for setting conservation priorities, but also constrained our ability to understand patterns in biodiversity. Obtaining a comprehensive measure of the spatial patterns of biodiversity is also hampered by the complexity of the concept (Purvis and Hector, 2000). For these reasons, conservation prioritization exercises often focus on univariate metrics, such as the number of species, to guide protection and restoration efforts (Brooks et al., 2006, Allen, 2008, Trebilco et al., 2011).
The total number of species (hereafter species richness) is a relatively simple and easy measure of an area's relevance to conserve biodiversity. There is solid evidence that species-rich places have increased ability to maintain key ecosystem services (e.g. food production, water quality maintenance, etc.), to recover from disturbances and to resist to invasions (Worm et al., 2006). The local species richness, however, is only one among many attributes of biodiversity. This means that choosing areas for protection on the basis of only species richness may be inadequate to represent, for example, small-ranged and endemic species, which often have idiosyncratic geographical distributions and a high propensity to become locally rare or extinct (Roberts et al., 2002, Orme et al., 2005). Because of this, the value of spatial conservation strategies is enhanced when measures of richness are associated with complementary biodiversity metrics, such as rarity and endemism (Fleishman et al., 2006).
Using the Mexican avifauna and South American anurans as models, Villalobos et al., 2013a, Villalobos et al., 2013b proposed a straightforward approach to define conservation priorities at large spatial scales integrating both richness and rarity. Species considered rare because of their restricted geographic ranges also tend to have relatively small populations – two attributes that make them more prone to extinction (Roberts and Hawkins, 1999). Hence, rarity per se has been considered a double jeopardy (Gaston, 1998). Rare species often have traits distinct from those of common species and are responsible for essential – and vulnerable – ecological functions in assemblage structuring and ecosystem functioning (Mouillot et al., 2013). Conservation efforts directed to locally rare species are important even if they are common elsewhere, because they can prevent the loss of essential parts for the functioning of local ecosystems, of genetic diversity and, ultimately, extinction events (Hunter and Hutchinson, 1994, Mouillot et al., 2013).
In this study, the geographic patterns of species richness and rarity of the estuarine fish fauna were mapped and integrated to identify regions of potential conservation value on the Brazilian coast (which encompasses the whole Brazilian Province, sensu Floeter et al., 2008). We also analyzed the effectiveness of the existing system of protected areas to represent these regions. The main goal was to investigate the following questions: (1) what are the most species-rich areas for estuarine fishes? (2) where are concentrated the estuarine fish species rarer in Brazil? (3) which areas have both high estuarine fishes richness and species with relatively small geographical ranges? (4) to what extent the existing protected areas cover these crucial regions and how one might make improvements? A secondary goal was to test whether different measures of biodiversity (species richness, endemism and rarity) are spatially congruent and efficient as surrogates for each other.
Section snippets
Database
A list of estuarine fish species in Brazil was compiled from (1) studies conducted in 31 estuaries distributed along the whole coast; (2) regional checklists, identification guides, and scientific collections (references in Appendix A1). Data collection was restricted to environments that, even loosely, meet the definition of estuary proposed by Day (1980), i.e., any “partially enclosed coastal body of water which is either permanently or periodically open to the sea and within which there is a
Results
Of the 412 estuarine fish species considered, 371 are Actinopterygii and 41 Elasmobranchii. The total number of species per latitudinal band ranged from 160 to 328 (mean ± SD = 281 ± 52 species). The species-richest bands are situated on the coast of the state of Rio de Janeiro, where 79.6% of all fish species included in this study are estimated to occur in a single band. The coast of Rio Grande do Sul (in temperate latitudes) has the lowest total richness (Fig. 2a). The number of endemic
Discussion
For the first time are described and elucidated the interrelationship between the geographic patterns of species richness, endemism and rarity of estuarine fish fauna along the Brazilian coast. Our results revealed that (1) centers of species richness and endemism of estuarine ichthyofauna are geographically incongruent; (2) the spatial pattern of rarity for all species is remarkably different from that found for endemic species; (3) the metrics analyzed (species richness, endemism and rarity)
Acknowledgements
This study is dedicated to Rogério L. Teixeira (in memoriam) for his vast legacy on the Brazilian biodiversity and for encouraging several researchers to take their first steps in Science. We are grateful to Maurício Noemberg (Universidade Federal do Paraná) for building the latitudinal bands and to the anonymous reviewers for their valuable comments. C.C.V. also thanks CAPES for financial support during the writing of this manuscript.
References (44)
- et al.
The mid-domain effect: geometric constraints on the geography of species richness
Trends Ecol. Evol.
(2000) - et al.
Utility and limitations of species richness metrics for conservation planning
Ecol. Indic.
(2006) - et al.
Extinction risk in the sea
Trends Ecol. Evol.
(1999) - et al.
Assessing the performance of the existing and proposed network of marine protected areas to conserve marine biodiversity in Chile
Biol. Conserv.
(2009) - et al.
Mapping species richness and human impact drivers to inform global pelagic conservation prioritization
Biol. Conserv.
(2011) - et al.
Setting priorities for the conservation of marine vertebrates in Brazilian waters
Ocean. Coast Manage
(2015) - et al.
Range-diversity plots for conservation assessments: using richness and rarity in priority setting
Biol. Conserv.
(2013) Conservation hotspots of biodiversity and endemism for Indo-Pacific coral reef fishes
Aquat. Conserv. Mar. Freshw. Ecosyst.
(2008)Freshwater Fish Distribution
(2007)- et al.
Global biodiversity conservation priorities
Science
(2006)
What is an estuary
S Afri J. Sci.
Spatial mismatch and congruence between taxonomic, phylogenetic and functional diversity: the need for integrative conservation strategies in a changing world
Ecol. Lett.
Modifying the t test for assessing the correlation between two spatial processes
Biometrics
ArcView GIS Ver. 9.3.1
Geographic variation in reef-fish assemblages along the Brazilian coast
Glob. Ecol. Biogeogr.
Atlantic reef fish biogeography and evolution
J. Biogeogr.
Rarity as double jeopardy
Nature
The virtues and shortcomings of parochialism: conserving species that are locally rare but globally common
Conserv. Biol.
Processes underpinning fish species composition patterns in estuarine ecosystems worldwide
J. Biogeogr.
Biogeographical region and environmental conditions drive functional traits of estuarine fish assemblages worldwide
Fish Fish.
The significance of geographic range size for spatial diversity patterns in Neotropical palms
Ecography
Global diversity hotspots and conservation priorities for sharks
PLoS One
Cited by (16)
Past and present conservation of south American estuaries
2023, Estuarine, Coastal and Shelf ScienceThe agony of choice: Species richness and range size in the determination of hotspots for the conservation of phyllostomid bats
2022, Perspectives in Ecology and ConservationCitation Excerpt :These plots have been useful to identify areas of importance for conservation, by simultaneously combining the species richness and their geographic rarity. This conceptual and methodological proposal has been applied to terrestrial and aquatic vertebrates (Vilar et al., 2017; Villalobos et al., 2013a). Also, combined with ecological niche models, these RD-plots have been used to assess changes in the distribution and alpha and beta diversity of plants, amphibians, and birds, under climate change scenarios (Prieto-Torres et al., 2020).
Variability in nearshore fish biodiversity indicators after a mining disaster in eastern Brazil
2022, Marine Environmental ResearchCitation Excerpt :The potential ecological effects of the disaster on estuarine and coastal fish assemblages remain, however, largely unknown (but see Andrades et al., 2020, 2021). In the present study, we measure well-established indicators to assess spatial and seasonal variation in the fish assemblage of the Doce river delta, a priority area for the conservation of estuarine fishes on the Brazilian coast (Vilar et al., 2017). We explore similarities and complementarities among indicators in revealing changes in fish assemblages and provide a baseline against which to assess the status and trends of fish biodiversity over time.
Overview of franciscana diet
2022, The Franciscana Dolphin: On the Edge of SurvivalAssessment of metal contamination in estuarine surface sediments from Dongying City, China: Use of a modified ecological risk index
2018, Marine Pollution BulletinCitation Excerpt :These rivers run through the city from south to north, and there are a large number of enterprises, such as the salt chemical industry, petroleum exploitation, petrochemical industry, machinery manufacturing, and metal processing, as well as several livestock farms and farmland on both sides of the rivers. The estuarine waters, with a water depth < 5 m, are ecologically and economically important due to their biological diversity including a variety of anadromous fishes, plankton, benthos (commercial shellfish species, etc.), and other organisms of economic and ecological value (Oursel et al., 2013; Vilar et al., 2017). Since 2008, the west of this area has been declared as a China Marine Special Conservation Area (MSCA) for the protection of its estuary shellfish ecosystem, with a watershed area of 396.23 km2.
The contribution of geographically common and rare species to the spatial distribution of biodiversity
2023, Global Ecology and Biogeography