Spatial structure in invasive Alliaria petiolata reflects restricted seed dispersal

Biswas, Shekhar R.; Wagner, Helene H.

doi:10.1007/s10530-015-0946-8

Cited by 10 publications

(10 citation statements)

References 39 publications

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“…The mean and median seed dispersal distances predicted by the 2Dt function were about 0.50 m, which is substantially less than the 1.28 m (range 1.03–1.63 m) predicted by Biswas & Wagner (2015) who used an experimental design similar to ours. However, the first seed traps in that study were placed 0.50 m from the point seed source which may have resulted in the majority of dispersed seeds being missed as our results indicate peak seed dispersal occurred at 0.35.…”

Section: Discussioncontrasting

confidence: 71%

Measuring short distance dispersal ofAlliaria petiolataand determining potential long distance dispersal mechanisms

Loebach

Anderson

2018

PeerJ

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IntroductionAlliaria petiolata, an herbaceous plant, has invaded woodlands in North America. Its ecology has been thoroughly studied, but an overlooked aspect of its biology is seed dispersal distances and mechanisms. We measured seed dispersal distances in the field and tested if epizoochory is a potential mechanism for long-distance seed dispersal.MethodsDispersal distances were measured by placing seed traps in a sector design around three seed point sources, which consisted of 15 second-year plants transplanted within a 0.25 m radius circle. Traps were placed at intervals ranging from 0.25–3.25 m from the point source. Traps remained in the field until a majority of seeds were dispersed. Eight probability density functions were fitted to seed trap counts via maximum likelihood. Epizoochory was tested as a potential seed dispersal mechanism for A. petiolata through a combination of field and laboratory experiments. To test if small mammals transport A. petiolata seeds in their fur, experimental blocks were placed around dense A. petiolata patches. Each block contained a mammal inclusion treatment (MIT) and control. The MIT consisted of a wood-frame (31 × 61× 31 cm) covered in wire mesh, except for the two 31 × 31 cm ends, placed over a germination tray filled with potting soil. A pan filled with bait was placed in the center of the tray. The control frame (11 × 31 × 61 cm) was placed over a germination tray and completely covered in wire mesh to exclude animal activity. Treatments were in the field for peak seed dispersal. In March, trays were moved to a greenhouse and A. petiolata seedlings were counted and then compared between treatments. To determine if A. petiolata seeds attach to raccoon (Procyon lotor) and white-tailed deer (Odocoileus virginianus) fur, wet and dry seeds were dropped onto wet and dry fur. Furs were rotated 180 degrees and the seeds that remained attached were counted. To measure seed retention, seeds were dropped on furs and rotated as before, then the furs were agitated for one hour. The seeds retained in the fur were counted.ResultsFor the seed dispersal experiment, the 2Dt function provided the best fit and was the most biologically meaningful. It predicted that seed density rapidly declined with distance from the point source. Mean dispersal distance was 0.52 m and 95% of seeds dispersed within 1.14 m. The epizoochory field experiment showed increased mammal activity and A. petiolata seedlings in germination trays of the MIT compared to control. Laboratory studies showed 3–26% of seeds were attached and retained by raccoon and deer fur. Retention significantly increased if either seed or fur were wet (57–98%).DiscussionWithout animal seed vectors, most seeds fall within a short distance of the seed source; however, long distance dispersal may be accomplished by epizoochory. Our data are consistent with A. petiolata’s widespread distribution and development of dense clusters of the species in invaded areas.

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Section: Discussioncontrasting

confidence: 71%

Measuring short distance dispersal ofAlliaria petiolataand determining potential long distance dispersal mechanisms

Loebach

Anderson

2018

PeerJ

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“…However, it should be noted that different processes may create similar spatial association and similar processes may create different spatial associations (Cale et al 1989, Dale andFortin 2014); and accordingly, different processes may create similar spatial association-trait dissimilarity relationship. While we did not focus on species' dispersal pattern, patchy dispersal could also create spatially aggregated pattern (Biswas and Wagner 2015) and corresponding spatial association-trait dissimilarity relationship. On the other hand, if the environmental filtering is the one and only reason for the observed species association-trait dissimilarity relationship, then one could expect no such relationship above the scale of environmental patchiness.…”

Section: Discussionmentioning

confidence: 99%

Negative relationship between interspecies spatial association and trait dissimilarity

Biswas

2018

Oikos

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Species’ response to environmental site conditions and neighborhood interactions are among the important drivers of species’ spatial distributions and the resultant interspecies spatial association. The importance of competition to interspecies spatial association can be inferred from a high degree of trait dissimilarity of the associated species, and vice versa for environmental filtering. However, because the importance of environmental filtering and competition in structuring plant communities often vary with spatial scale and with plant life stage, the species’ spatial association–trait dissimilarity relationship should vary accordingly. We tested these assumptions in a fully mapped 50‐ha subtropical evergreen forest of China, where we assessed the degrees of interspecies spatial associations between adult trees and between saplings at two different spatial scales (10 m versus 40 m) and measured the degrees of trait dissimilarity of the associated species using six traits (leaf area, specific leaf area, leaf dry‐matter content, wood density, wood dry‐matter content and maximum height). Consistent across spatial scales and plant life stages, the degree of interspecies spatial association and the degree of overall trait dissimilarity (i.e. all six traits together) were negatively correlated, suggesting that environmental filtering might help assemble functionally similar species in the forest under study. However, when we looked into the spatial association–trait dissimilarity relationship for individual traits, we found that the relationships between interspecies spatial associations and the dissimilarity of wood density and dry‐matter content were significant for adults but not for saplings, suggesting the importance of wood traits in species’ survival during ontogeny. We conclude that processes shaping interspecies spatial association are spatial scale and plant life stage dependent, and that the distributions of functional traits offer useful insights into the processes underlying community spatial structure.

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“…This light gap differed from the one colonized by Alliaria, however, in occurring on a north-facing slope and in an area with very low cover and frequency of Alliaria to begin with (Figs. 3, 4), so propagule pressure and dispersal rate are likely to be very low, as well, given the low dispersal distance of most Alliaria seeds (Biswas and Wagner 2015).…”

Section: Environmental Correlatesmentioning

confidence: 99%

“…Allocation to seed production by Alliaria is correspondingly high: Population averages are commonly well over 100 seeds per plant (Byers andQuinn 1998, Nuzzo 1999), and large plants are capable of producing thousands of seeds (Rodgers et al 2008a, Phillips-Mao et al 2014. Seeds disperse by explosive dehiscence, mostly falling 1-2 m from the parent plant, with occasional longer-distance dispersal possible via running water and animal coats (Nuzzo 1993, 1999, Biswas and Wagner 2015, Loebach and Anderson 2018. The propagule pressure resulting from this high individual fecundity and concentrated seed rain is thought to be an important contributor to the ability of Alliaria populations to naturalize in temperate forests Battles 2009, Dornbush andHahn 2013), particularly in communities in which the resident species are dispersal-limited (Dornbush and Hahn 2013), or in which disturbance has recently enhanced availability of resources such as light (Eschtruth and Battles 2009).…”

Section: Phenology and Inter-annual Regenerationmentioning

confidence: 99%

Comparison of the non‐native herbAlliaria petiolatawith dominant native herbs in microhabitats of a Midwestern forest

et al. 2019

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A mechanistic understanding of the causes of naturalization in terrestrial plant communities, and the consequences for associated ecosystems, relies on understanding whether and how native and non‐native plant traits differ. Traits of non‐native plants may either help them compete or avoid competition with natives, and depending on their interaction with the native community, the non‐native may act as more or less of an active driver vs. a passive passenger of change in the native ecosystem. Trait comparisons between native and non‐native plants are often laboratory‐based, providing insights that can be difficult to apply to natural communities. Studies of the impacts of non‐native plants, by contrast, are generally performed in natural communities, but usually do not compare observed impacts of the non‐natives with those exerted by dominant natives on each other and the community. Thus, the likely relative disruption of the non‐native to the community is unclear. In a four‐year observational study conducted at the microhabitat scale in the herbaceous layer of a Midwestern oak forest, we compared the non‐native herb Alliaria petiolata (garlic mustard) with dominant native herbaceous species in terms of correlational patterns related to three broad categories of traits: (1) environmental correlates (light, topography, soil nutrients) with presence and cover, (2) inter‐annual regeneration and phenology, and (3) associations with other species (competition and herbivory). We found that Alliaria differed strongly from dominant native herbs in all three categories. Compared with native herbs, Alliaria was more strongly associated with south‐facing slopes and high nutrient levels, displayed earlier phenology and enhanced dispersal ability, and was strongly avoided by the generalist native herbivore, Odocoileus virginianus (white‐tailed deer). Despite well‐described allelopathic effects of Alliaria on mycorrhizae and mycorrhizal plants, we found little evidence to suggest that Alliaria had negative interactions with native plants that were stronger than those of native community members. Overall, our data suggest that naturalization of Alliaria in this site is primarily due to differences from native plants in phenology, dispersal capability, and avoidance of herbivory, and that Alliaria is therefore more likely to be acting as a passenger than as a driver of change in our site.

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Spatial structure in invasive Alliaria petiolata reflects restricted seed dispersal

Cited by 10 publications

References 39 publications

Measuring short distance dispersal ofAlliaria petiolataand determining potential long distance dispersal mechanisms

Measuring short distance dispersal ofAlliaria petiolataand determining potential long distance dispersal mechanisms

Negative relationship between interspecies spatial association and trait dissimilarity

Comparison of the non‐native herbAlliaria petiolatawith dominant native herbs in microhabitats of a Midwestern forest

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