Interesting Paper

An interesting paper examining differing flower phenology and the visiting pollinator community.

Flower-visiting insect communities on two closely related Rhododendron species flowering in different seasons

Shinji Sugiura

Arthropod-Plant Interactions (2012) 6:333–344

Abstract To determine the effects of flowering season on the community structure and dynamics of flower visitors, I examined annual and hourly variation in flower-visiting insects on two Rhododendron species in a deciduous secondary forest in central Japan. Rhododendron reticulatum flowers from late March to mid-April, whereas R. macrosepalum flowers from late April to late May. Bagged and hand-pollination experiments indicated that outcrossing by flower visitors was important for the pollination of both R. reticulatum and R. macrosepalum. Pollinator and pollen limitation were detected in both Rhododendron species, although the extent of both differed between the two species. The flowers of both Rhododendron species were visited by insects of diverse taxa, including Hymenoptera, Diptera and Lepidoptera. The composition of flower visitors differed between R. reticulatum and R. macrosepalum, although a few species visited both of them. The beefly Bombylius major (Diptera: Bombyliidae) most frequently visited R. reticulatum, whereas the bumblebee Bombus ardens ardens (Hymenoptera: Apidae) most frequently visited R. macrosepalum. Hourly changes in the number of flower visitors also differed between R. reticulatum and R. macrosepalum; insects visited R. reticulatum flowers less frequently in the morning than in the afternoon, whereas insect visitations to R. macrosepalum flowers did not differ between morning and afternoon. Differences in both insect community structure and hourly changes of visitations between the two Rhododendron species occurred annually and may be related to the life history of the abundant visitor species as well as flowering phenology.

Paper Sept 2012

This is an early view in BI. About the most ever studied invasive tree.


Differences in cold hardiness between introduced populations of an invasive tree
Isaac Park, Saara J. DeWalt, Evan Siemann, William E. Rogers


Abstract The potential for populations of exotic invasive plants to differ in their response to stressful environmental conditions is an underexplored issue in determining invasive species’ range limits. Introduced genotypes may differ in response to climatic, edaphic, or biotic factors within their introduced range leading to differences in potential ranges among populations.
We examined differences in cold hardiness (resistance and tolerance to winter conditions and freeze events) among Chinese tallow tree (Triadica sebifera (L.) Small) seeds and seedlings from two genetically distinct populations in the northernmost portion of its introduced U.S. range (North Carolina and South Carolina). Seed germination from these two
sources was compared between fall plantings (mimicking natural dispersal timing) and spring plantings (occurring post-frost) as well as among areas within and inland of Chinese tallow’s core coastal distribution in South Carolina. Overwinter seedling survival and damage were also assessed among seedlings planted in the piedmont of South Carolina and following artificial freeze events in the lab. Seeds and seedlings from South Carolina sources showed greater reductions in germination success by inland winters, greater winter damage in field plantings in the piedmont, and lower survival after prolonged freezes than those from North Carolina. These results indicate that differences in cold hardiness exist among introduced populations of Chinese tallow and suggest that genotypes from North Carolina possess greater
potential for expansion into areas with more severe winters. Differences among introduced populations should be considered when evaluating the potential range expansion of Chinese tallow and other invasive species.

Interesting Paper

Presence of an invasive plant species alters pollinator visitation to a native. BI 2012: Vashti M. King • Risa D. Sargent

Abstract: The degree to which pollinator-mediated interactions assist or impede plant invasions is currently poorly understood. Here we describe the findings of an experiment designed to investigate how pollinator-mediated interactions between invasive Lythrum salicaria (Purple loosestrife) and a closely related native North American species, Decodon verticillatus (Swamp loosestrife) are influenced by the stage of invasion (i.e., early or late). By comparing pollinator preference and constancy to plants in experimentally introduced arrays of L. salicaria and D. verticillatus in invaded and uninvaded communi- ties, we were able to simulate the ecological implica- tions of two different stages of L. salicaria invasion. Invasion status had no significant effect on pollinator visitation to L. salicaria and D. verticillatus when all pollinator taxa were considered together. However, when bumblebees, the dominant pollinator at all sites, were considered alone, we found a significant inter- action between pollinator preference and the invasion status of the site, with D. verticillatus preferred at uninvaded sites only, and no preference exhibited at invaded sites. In addition, for all pollinator taxa, we found that interspecific pollinator movements were overrepresented at uninvaded sites and underrepre- sented at invaded sites, suggesting that heterospecific pollen deposition could be a significant impediment to pollinator-mediated reproduction for both species in the early stages of an invasion. We discuss the potential consequences of our findings to the estab- lishment of animal-pollinated invasive plants and the persistence of native species in the face of invasion.