Abstract
Biodiversity hotspots can serve as protected areas that aid in species conservation. Long-term monitoring of multiple taxonomic groups within biodiversity hotspots can offer insight into factors influencing their dynamics. Mussels (Bivalvia: Unionidae) and fish are highly diverse and imperiled groups of organisms with contrasting life histories that should influence their response to ecological factors associated with local and global change. Here we use historical and contemporary fish and mussel survey data to assess fish and mussel community changes over a 33 year period (1986–2019) and relationships between mussel abundance and their host fish abundance in Bogue Chitto Creek, a tributary of the Alabama River and a biodiversity hotspot. Mussel abundance declined by ~80% and community composition shifted, with eight species previously recorded not found in 2019, and a single individual of the endangered Pleurobema decisum. Fish abundances increased and life history strategies in the community appeared stable and there was no apparent relationship between mussel declines and abundance of host fish. Temporal variation in the proportion of life history traits composing mussel assemblages was also indicative of the disturbances specifically affecting the mussel community. However, changes and declines in mussel assemblages in Bogue Chitto Creek cannot be firmly attributed to any specific factor or events because of gaps in historical environmental and biological data. We believe that mobility differences contributed to differential responses of fish and mussel communities to stressors including habitat degradation, recent droughts and invasive species. Overall, our work indicates that monitoring biodiversity hotspots using hydrological measurements, standardized survey methods and monitoring invasive species abundance would better identify the effects of multiple and interactive stressors that impact disparate taxonomic groups in freshwater ecosystems.
Highlights
Climate and land use change, an increase in human population, invasive species, and direct exploitation increasingly threaten global and local biodiversity [1,2]
Despite the lack of relationships between host fish abundance and freshwater mussels, we evaluated habitat characteristics that could be potentially affecting both populations
Our study shows substantial differences in the vulnerability of two distinct taxonomic groups which we hypothesize is attributed to differences in mobility
Summary
Climate and land use change, an increase in human population, invasive species, and direct exploitation increasingly threaten global and local biodiversity [1,2]. ‘Biodiversity hotspots’ are commonly delineated to aid in conservation strategies because they are species rich, with high levels of endemism, and are threatened by human activities [3]. Designated biodiversity hotspots may not reflect cyclical or periodic natural disturbance regimes, or possibly obscure substantial biodiversity declines with increasing human pressures [5]. Disparate taxonomic groups (e.g., vertebrates vs invertebrates) may not benefit from protected areas [6,7]. Sampling multiple taxonomic groups inhabiting designated biodiversity hotspots through time set ecological baselines, captures biodiversity trends, highlights areas of conservation concern, determines program outcomes, and can help distinguish between anthropogenic and natural disturbances influencing community turnover [8,9]
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