Research themes: Maintaining biodiversity

Understanding the factors that maintain biodiversity is an enduring challenge in community ecology. Much of our research focuses on resolving the roles of environmental disruptions (e.g., disturbance) and species interactions (e.g., competition, facilitation) in promoting or constraining species coexistence. We are also interested in the role of spatial processes, such as dispersal and patchy disturbances, in mediating diversity.

Key findings

Repeated loss of foundation species can outweigh the influence of less-frequent but severe disturbances for biodiversity

  • Disturbance regimes vary in both their frequency and severity, however investigations have often been incapable of disentangling the effects of these disturbance attributes. 

  • Disturbance frequency outweighs severity in structuring kelp forest communities (Castorani et al. 2018). Frequent loss of giant kelp strongly alters community guilds in a manner consistent with their reliance on physical, trophic, and habitat resources. 

  • In contrast, variation in disturbance severity has the strongest effects on highly mobile consumers capable of migrating to more suitable habitat.

Invasive species structure native biodiversity through direct and indirect effects

  • The invasive Asian nest mussel (Arcuatula senhousia) directly impacts native bivalves through exploitative competition for resources and habitat modification (Castorani and Hovel 2015). By attracting native predators, invasive mussels also indirectly increase predation of native clams, especially for poorly-defended species. 

  • Therefore, non-native prey can change the behavior of native predators and harm native competitors through apparent competition. In fact, the vulnerability of invasive prey to predation can exacerbate impacts on their native competitors.

  • The success of this invader may also be partly attributable to its lack of naïvity to native predators, as it shows selective anti-predation behaviors to different consumers (Castorani and Hovel 2016). 

Environmental conditions mediate habitat modification and species interactions

  • Theory predicts that environmental context mediates the sign and strength of impacts by habitat-modifying organisms capable of simultaneously ameliorating and exacerbating multiple stressors.

  • Light controls mussel habitat modification and impacts on seagrass via stress pathways. Specifically, light intensity interacts with mussel density to structure oxygen fluxes and drive sulfide intrusion of seagrass tissues (Castorani et al. 2015). 

  • Light mediates the effect of mussels on nitrogen and energy metabolism, responses to sulfide toxicity, and tissue degradation (Hasler-Sheetal et al. 2016).

  • These findings suggest that coastal eutrophication is likely to shift bivalve effects on seagrasses from positive to negative.

Disturbance maintains spatial coexistence through a competition-colonization trade-off

  • Theory predicts that disturbance can facilitate coexistence between species competing for limited resources.

  • In field surveys and experiments, disturbance to competitively-dominant, short-dispersing seagrass enhances spatial coexistence with competitively-inferior, broad-dispersing burrowing shrimp (Castorani et al. 2014).
  • In population models, disturbance size and frequency interact to structure coexistence through the spatial storage effect (Castorani & Baskett 2020). Supporting theory, intermediate disturbance enhances biodiversity.
  •  Hence, disturbance size, frequency, and their interaction can mediate landscape-scale biodiversity by altering the duration of time over which inferior competitors can escape competitive exclusion.

Related publications:

  • Smith, R.S., S.L. Cheng, and M.C.N. Castorani. In press. Meta-analysis of ecosystem services associated with oyster restoration. Conservation Biology.
  • Smith, R.S., B. Lusk, and M.C.N. Castorani. 2022. Restored oyster reefs match multiple functions of natural reefs within a decade. Conservation Letters 15(4):e12883. [PDF]
  • Hogan, S., E.A.K. Murphy, M.P. Volaric, M.C.N. Castorani, P. Berg, and M.A. Reidenbach. 2022. Influence of oyster reefs on infauna and sediment spatial distributions within intertidal mudflats. Marine Ecology Progress Series 686:91–106.

  • Lamy, T., N.I. Wisnoski, R. Andrade, M.C.N. Castorani, A. Compagnoni, N. Lany, L. Marazzi, S. Record, C.M. Swan, J.D. Tonkin, N.M. Voelker, S. Wang, P.L. Zarnetske, and E.R. Sokol. 2021. The dual nature of metacommunity variability. Oikos 130(12):2078–2092[PDF]

  • Walter, J.A., L.G. Shoemaker, N.K. Lany, M.C.N. Castorani, S.B. Fey, J.C. Dudney, L.A. Gherardi, C. Portales-Reyes, A.L. Rypel, K.L. Cottingham, K.N. Suding, D.C. Reuman, and L.M. Hallett. 2021. The spatial synchrony of species richness and its implications for ecosystem stability. Ecology 102(11):e03486[PDF]
  • O’Brien, M., C.A. Smith, E.R. Sokol, C. Gries, N. Lany, S. Record, and M.C.N. Castorani. 2021. ecocomDP: A flexible data design pattern for ecological community survey data. Ecological Informatics 64:101374. [PDF]
  • Record, S., N.M. Voelker, P.L. Zarnetske, N.I. Wisnoski, J.D. Tonkin, C. Swan, L. Marazzi, N. Lany, T. Lamy, A. Compagnoni, M.C.N. Castorani, R. Andrade, and E.R. Sokol. 2021. Novel insights to be gained from applying metacommunity theory to long-term, spatially replicated biodiversity data. Frontiers in Ecology and Evolution 8:612794. [PDF]
  • Zhao, L., S. Wang, L.M. Hallett, A.L. Rypel, L.W. Sheppard, M.C.N. Castorani, L.G. Shoemaker, K.L. Cottingham, K. Suding, and D.C. Reuman. 2020. A new variance ratio metric to detect the timescale of compensatory dynamics. Ecosphere 11(5):e03114. [PDF]
  • Castorani, M.C.N. and M.L. Baskett. 2020. Disturbance size and frequency mediate the coexistence of benthic spatial competitors. Ecology 101(1):e02904[PDF]
  • Castorani, M.C.N., D.C. Reed, and R.J. Miller. 2018. Loss of foundation species: disturbance frequency outweighs severity in structuring kelp forest communities. Ecology 99(11):2442–2454. [PDF]
  • Hasler-Sheetal, H., M.C.N. Castorani, R.N. Glud, D.E. Canfield, and M. Holmer. 2016. Metabolomics reveals cryptic interactive effects of species interactions and environmental stress on nitrogen and sulfur metabolism in seagrass. Environmental Science & Technology 50(21):11602–11609. [PDF]
  • Castorani, M.C.N., and K.A. Hovel. 2016. Native predator chemical cues induce anti-predation behaviors in an invasive marine bivalve. Biological Invasions 18(1):169–181. [PDF]
  • Castorani, M.C.N., R.N. Glud, H. Hasler-Sheetal, and M. Holmer. 2015. Light indirectly mediates bivalve habitat modification and impacts on seagrass. Journal of Experimental Marine Biology and Ecology 472:41–53. [PDF]
  • Castorani, M.C.N., and K.A. Hovel. 2015. Invasive prey indirectly increase predation on their native competitors. Ecology 96(7):1911–1922. [PDF]
  • Castorani, M.C.N., K.A. Hovel, S.L. Williams, and M.L. Baskett. 2014. Disturbance facilitates the coexistence of antagonistic ecosystem engineers in California estuariesEcology 95(8):2277–2288. [PDF]