Investigating Seed Dispersal Distances And Long Distance Dispersal Mechanisms Of The Invasive Plant, Alliaria Petiolata

Alliaria petiolata, an herbaceous plant, has aggressively invaded North American woodlands. It has been extensively studied to understand why it is a successful invader, but certain aspects of its biology have been understudied such as seed dispersal distances and long distance dispersal mechanisms (LDDM). My thesis experimentally measured A. petiolata seed dispersal distances and determined if epizoochory (external animal transport) is a LDDM. To measure dispersal distances, seed traps were placed around three A. petiolata seed point sources to capture dispersed seeds at increasing distances away from the point sources. Eight mathematical functions that describe dispersal distances were fitted to seed counts in traps via maximum likelihood. The lognormal and 2Dt functions were selected for analyses and both predicted that seed density rapidly declined as distance increased with mean dispersal distances of 0.56 and 0.52m and 95% of seeds dispersed within 1.22 and 1.14m, respectively. To determine if epizoochory is a LDDM, experimental blocks were placed around seven dense A. petiolata patches in summers 2013-2014. Each block contained a mammal inclusion treatment (MIT), which increased small mammal activity over a germination tray with potting soil, and a control, which excluded mammal activity. Seeds dispersed into trays were germinated and counted. The increased mammal activity in the MIT resulted in significantly more A. petiolata seedlings than the control. Laboratory studies determined if A. petiolata seeds can attach and be retained by raccoon (Procyon lotor) and white-tailed deer (Odocoileus virginianus) fur, common woodland mammals. A small proportion (3-26%) of seeds attached to and were retained within raccoon and deer fur. Attachment and retention significantly increased if either the seed or fur was wet (57-98%). These results are the first to experimentally determine that epizoochory is a seed dispersal mechanism of A. petiolata with raccoon and deer as likely dispersal agents

Dataset for Response of the Invasive Alliaria Petiolata to Extreme Temperatures and Drought

Alliaria petiolata, a strict biennial in North America, can have annual alternating high abundance of rosettes and flowering plants. We monitored changes in abundance of rosettes and flowering plants in permanent plots (2004 to 2014). Three times during our study the alternating yearly cycle was not observed (2007-2008, 2008-2009, and 2013-2014). We concluded stochastic Extreme Climate Events (ECEs), deviating from long-term climatic data norms (10th or 90th. percentile), likely caused negative organism responses. Long-term data from a local NOAA station located 25 km from our study site included monthly data (1) total precipitation, (2) number of days with \u3e 0.13 cm precipitation, and (3) mean and minimum temperatures. September 2007 met criteria for ECEs for all monthly variables. We first observed A. petiolata on our study site in 1988 and by the early 1990’s it was abundant. To determine if September 2007 significantly differed from other Septembers (1984-2014) we used six variables related to drought: (1) total precipitation, (2) number of days with precipitation, (3) number of contiguous days without precipitation, (4) mean monthly temperature, (5) mean maximum daily temperature, and (6) the number of days with temperatures \u3e 30 o C. The first two variables likely increase plant stress as they decrease, whereas stress declines as the remaining variables decrease. We used the six variables to generate a Principal Component Analysis (PCA) biplot. Axes 1 and 2 accounted for 74.3% of the variance. Record-breaking minimum temperatures (ECEs) for January (2009) and February-March (2014) likely reduced rosette abundance and disrupted reestablishment of alternating high abundance of rosettes and flowering plants. Our data suggest that a single ECE variable, minimum temperature, and multiple ECE variables related to drought likely had negative effects on A. petiolata

Measuring short distance dispersal of Alliaria petiolata and determining potential long distance dispersal mechanisms

Introduction Alliaria 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. Methods Dispersal 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. Results For 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%). Discussion Without 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

Acceptance and commitment therapy for late-life treatment-resistant generalised anxiety disorder : a feasibility study

Background: Generalised anxiety disorder (GAD) is the most common anxiety disorder in older people. First-line management includes pharmacological and psychological therapies, but many do not find these effective or acceptable. Little is known about how to manage treatment-resistant generalised anxiety disorder (TR-GAD) in older people. Objectives: To examine the acceptability, feasibility and preliminary estimates of the effectiveness of acceptance and commitment therapy (ACT) for older people with TR-GAD. Participants: People aged ≥65 years with TR-GAD (defined as not responding to GAD treatment, tolerate it or refused treatment) recruited from primary and secondary care services and the community. Intervention: Participants received up to 16 one-to-one sessions of ACT, developed specifically for older people with TR-GAD, in addition to usual care. Measurements: Co-primary outcomes were feasibility (defined as recruitment of ≥32 participants and retention of ≥60% at follow-up) and acceptability (defined as participants attending ≥10 sessions and scoring ≥21/30 on the satisfaction with therapy subscale). Secondary outcomes included measures of anxiety, worry, depression and psychological flexibility (assessed at 0 and 20 weeks). Results: Thirty-seven participants were recruited, 30 (81%) were retained and 26 (70%) attended ≥10 sessions. A total of 18/30 (60%) participants scored ≥21/30 on the satisfaction with therapy subscale. There was preliminary evidence suggesting that ACT may improve anxiety, depression and psychological flexibility. Conclusions: There was evidence of good feasibility and acceptability, although satisfaction with therapy scores suggested that further refinement of the intervention may be necessary. Results indicate that a larger-scale randomised controlled trial of ACT for TR-GAD is feasible and warranted