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1) Urbanization may lead to changes in local richness (alpha diversity) or in community composition (beta diversity), although the direction of change can be challenging to predict. For instance, introduced species may offset the loss of native specialist taxa, leading to no change in alpha diversity in urban areas, but decreased beta diversity (i.e., more homogenous community structure). Alternatively, because urban areas can have low connectivity and high environmental heterogeneity between sites, they may support distinct communities from one another over small geographic distances. 2) Wetlands and ponds provide critical ecosystem services and support diverse communities, making them important systems in which to understand consequences of urbanization. To determine how urban development shapes pond community structure, we surveyed 68 ponds around Madison, Wisconsin, USA, which were classified as urban, greenspace, or rural based on surrounding land use. We evaluated the influence of local abiotic factors, presence of nonnative fishes, and landscape characteristics on alpha diversity of aquatic plants, macroinvertebrates, and vertebrates. We also analyzed whether surrounding land cover was associated with changes in community composition and/or the presence of specific taxa. 3) We found a 23% decrease in mean richness (alpha diversity) from rural to urban pond sites, and a 15% decrease in richness from rural to urban greenspace pond sites. Among landscape factors, observed pond richness was negatively correlated with adjacent developed land and mowed lawns, as well as greater distances to other waterbodies. Among pond level factors, habitat complexity was associated with increased richness, while the presence of invasive fish was associated with decreased richness. 4) Beta diversity was relatively high for all ponds due to turnover in composition between sites. Urban ponds supported more introduced species, lacked a subset of native species found in rural ponds, and had slightly higher beta diversity than greenspace and rural ponds. 5) Synthesis and Applications: Integrating ponds into connected greenspaces comprised of native vegetation (rather than mowed grass), preventing nonnative fish introductions, and promoting habitat complexity may mitigate negative effects of urbanization on aquatic richness. The high beta diversity of distinct pond communities emphasizes their importance to biodiversity support in urban environments, despite being small in size and rarely incorporated into urban conservation planning.
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Pawpaws prevent predictability: A locally dominant tree alters understory beta‐diversity and community assembly
Abstract While dominant species are known to be important in ecosystem functioning and community assembly, biodiversity responses to the presence of dominant species can be highly variable. Dominant species can increase the importance of deterministic community assembly by competitively excluding species in a consistent way across local communities, resulting in low site‐to‐site variation in community composition (beta‐diversity) and nonrandom community structure. In contrast, dominant species could increase the importance of stochastic community assembly by reducing the total number of individuals in local communities (community size), resulting in high beta‐diversity and more random community structure. We tested these hypotheses in a large, temperate oak‐hickory forest plot containing a locally dominant tree species, pawpaw (Asimina triloba; Annonaceae), an understory tree species that occurs in dense, clonal patches in forests throughout the east‐central United States. We determined how the presence of pawpaw influences local species diversity, community size, and beta‐diversity by measuring the abundance of all vascular plant species in 1 × 1‐m plots both inside and outside pawpaw patches. To test whether the presence of pawpaw influences local assembly processes, we compared observed patterns of beta‐diversity inside and outside patches to a null model in which communities were assembled at random with respect to species identity. We found lower local species diversity, lower community size, and higher observed beta‐diversity inside pawpaw patches than outside pawpaw patches. Moreover, standardized effect sizes of beta‐diversity from the null model were lower inside pawpaw patches than outside pawpaw patches, indicating more random species composition inside pawpaw patches. Together these results suggest that pawpaw increases the importance of stochastic relative to deterministic community assembly at local scales, likely by decreasing overall numbers of individuals and increasing random local extinctions inside patches. Our findings provide insights into the ecological processes by which locally dominant tree species shape the assembly and diversity of understory plant communities at different spatial scales.
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- PAR ID:
- 10575158
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Ecosphere
- Volume:
- 16
- Issue:
- 1
- ISSN:
- 2150-8925
- Subject(s) / Keyword(s):
- Asimina triloba beta-diversity community assembly community size competition dominant species ecological drift forest herbs null model species interactions stochasticity temperate forest
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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1) Urbanization may lead to changes in local richness (alpha diversity) or in community composition (beta diversity), although the direction of change can be challenging to predict. For instance, introduced species may offset the loss of native specialist taxa, leading to no change in alpha diversity in urban areas, but decreased beta diversity (i.e., more homogenous community structure). Alternatively, because urban areas can have low connectivity and high environmental heterogeneity between sites, they may support distinct communities from one another over small geographic distances. 2) Wetlands and ponds provide critical ecosystem services and support diverse communities, making them important systems in which to understand consequences of urbanization. To determine how urban development shapes pond community structure, we surveyed 68 ponds around Madison, Wisconsin, USA, which were classified as urban, greenspace, or rural based on surrounding land use. We evaluated the influence of local abiotic factors, presence of nonnative fishes, and landscape characteristics on alpha diversity of aquatic plants, macroinvertebrates, and vertebrates. We also analyzed whether surrounding land cover was associated with changes in community composition and/or the presence of specific taxa. 3) We found a 23% decrease in mean richness (alpha diversity) from rural to urban pond sites, and a 15% decrease in richness from rural to urban greenspace pond sites. Among landscape factors, observed pond richness was negatively correlated with adjacent developed land and mowed lawns, as well as greater distances to other waterbodies. Among pond level factors, habitat complexity was associated with increased richness, while the presence of invasive fish was associated with decreased richness. 4) Beta diversity was relatively high for all ponds due to turnover in composition between sites. Urban ponds supported more introduced species, lacked a subset of native species found in rural ponds, and had slightly higher beta diversity than greenspace and rural ponds. 5) Synthesis and Applications: Integrating ponds into connected greenspaces comprised of native vegetation (rather than mowed grass), preventing nonnative fish introductions, and promoting habitat complexity may mitigate negative effects of urbanization on aquatic richness. The high beta diversity of distinct pond communities emphasizes their importance to biodiversity support in urban environments, despite being small in size and rarely incorporated into urban conservation planning.more » « less
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- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/ecs2.70115
