Latitudinal trends in the structure, similarity and beta diversity of plant communities invaded by Alternanthera philoxeroides in heterogeneous habitats

Abstract

Variations in latitudinal gradients could lead to changes in the performance and ecological effects of invasive plants and thus may affect the species composition, distribution and interspecific substitution of native plant communities. However, variations in structure, similarity and beta (β) diversity within invaded communities across latitudinal gradients in heterogeneous habitats remain unclear. In this study, we conducted a two-year field survey along 21°N to 37°N in China, to examine the differential effects of the amphibious invasive plant Alternanthera philoxeroides on native plant communities in terrestrial and aquatic habitats. We compared the differences in the invasion importance value (IV), species distribution, community similarity (Jaccard index and Sorenson index) and β diversity (Bray−Curtis index and βsim index) between terrestrial and aquatic communities invaded by A. philoxeroides, as well as analyzed their latitudinal trends. We found that the IV of A. philoxeroides and β diversity in aquatic habitats were all significantly higher than that of terrestrial, while the terrestrial habitat had a higher community similarity values. The aquatic A. philoxeroides IV increased with increasing latitude, while the terrestrial IV had no significant latitudinal trend. With increasing latitude, the component proportion of cold- and drought-tolerant species in the terrestrial communities increased, and the dominant accompanying species in the aquatic communities gradually changed from hygrophytes and floating plants to emerged and submerged plants. In addition, the aquatic communities had lower community similarity values and higher β diversity in higher latitudinal regions, while terrestrial communities had the opposite parameters in these regions. Our study indicates that the bioresistance capacities of the native communities to invasive A. philoxeroides in heterogeneous habitats are different; A. philoxeroides invasion leads to higher community homogenization in terrestrial habitats than in aquatic habitats, and terrestrial communities experience more severe homogenization in higher latitudinal regions. These findings are crucial for predicting the dynamics of invasive plant communities under rapid global change.

Niche Characteristics of Alternanthera philoxeroide-Invaded Plant Communities in Heterogeneous Habitats and Their Latitudinal Trends

“…From July to August of 2019-2021, the time of year during which the growth period of plant species is vigorous, we selected sites that were invaded by A. philoxeroides over an area of more than 100 m 2 to set the sampling plots, and the plots contained low (A. philoxeroides coverage < 40%), moderate (A. philoxeroides coverage was 40%-60%) and heavy (A. philoxeroides coverage > 60%) invaded levels. Starting from 21 N-37 • N) [34,36,39]. Five terrestrial plots were set along each latitudinal cluster, and five aquatic plots were also set in areas with similar habitat conditions along the same latitudinal cluster [35].…”

“…Neutral theory states that species similarity rather than species difference contributes to high community diversity; thus, continuous biointeractions among multiple species in terrestrial A. philoxeroides communities promote coexistence groups with high niche similarity [49]. In addition, Wu et al (2022) found that A. philoxeroides invasions caused higher community homogenization in terrestrial habitats than in aquatic habitats, and functional groups of Gramineae and Compositae that have strong invasion resistance widely exist in the community [34], which causes the plant species in terrestrial habitats to have closer geographical affinity and facilitates their convergent evolution. Moreover, environmental filtering caused by strong disturbances (e.g., human disturbances and insect feeding) in terrestrial habitats have led to the repeated colonization of plant species in the same species pool, which have caused similar species to show obvious aggregation and thus facilitated the coexistence of species with high niche similarity [19].…”

“…The alligator weed Alternanthera philoxeroides, a type of noxious invasive weed with clonal growth, is native to South America and has extensively invaded the United States, Australia, South Africa, China and other parts of the world [34]. A. philoxeroides is an amphibious invader, and in China it has invaded aquatic and terrestrial habitats in more than 20 provinces, causing serious damage to ecological environments and economic development [35].…”

“…In flooded environments, A. philoxeroides increases the diameter of its stolon to strengthen its interspecific competitiveness [38]. In addition, with increasing latitudes in China, aquatic A. philoxeroides communities have higher β-diversity, while terrestrial A. philoxeroides communities have higher similarity [34]. However, the niche characteristics of A. philoxeroides and its accompanying species at large spatial scales are unclear.…”