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Abstract Detail

Conservation Biology

Naczi, Robert [1].

Documenting Floristic Change in the Northeastern U.S.A., and its Implications for Conservation.

Floristic change is the increase or decrease in numbers of populations and/or individuals of plant species relative to a historic baseline. Previous studies in eastern North America have investigated relatively small geographic areas and often targeted rare species. This study focused on common native flowering plant species in a large region of the northeastern U.S.A.: Connecticut and southern New York south to southern Maryland. In this project, I tested the hypotheses that 1) floristic change has occurred in common species, and 2) both increases and decreases in numbers of populations have occurred. Herbarium specimens provided data to test these hypotheses. To investigate levels of collection effort, I studied six herbaria to compare numbers of specimens for each of seven species collected during two different time periods of the same duration. Four herbaria had even collection effort across the time periods, based on no statistically significant difference in numbers of vouchered populations for 1930-1949 vs. 1990-2009. These four herbaria provided geographic coverage for investigating floristic change in a set of taxonomically, morphologically, and ecologically diverse species common and widespread in northeastern North America---84 species belonging to 42 families, including herbs, vines, shrubs, and trees that grow in sunny, shady, wet, and dry habitats. The majority of the studied species (61 of 84 species, 73%) showed no statistically significant difference in population numbers across the region between the two time periods. Of the remainder, population numbers for 2 of 84 species (2%) significantly increased relative to the earlier time period, and 21 of 84 species (25%) significantly decreased. For decliners, decreases in the numbers of collections during the recent time period are 61−88% (mean = 71%) relative to the earlier time period. Currently, only 20% of the decliners are considered of conservation concern by the focal states. Decliners are geographically, ecologically, phylogenetically, and morphologically widespread and variable, making it unlikely that land-use changes or maladaptive traits are responsible for declines. Results of this study indicate floristic change, mostly decrease in population numbers, has occurred in a significant proportion of common flowering plant species native to the northeastern U.S.A over a recent 60-year time period. This study underscores the importance of conservation strategy that assesses and monitors status of plant species perceived as common, before their survival becomes questionable.

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1 - The New York Botanical Garden, 2900 Southern Blvd., Bronx, NY, 10458, USA

Flowering plants
Landscape-scale vegetation change
Floristic change

Presentation Type: Oral Paper
Session: 36, Conservation Biology
Location: Sundance 1/Omni Hotel
Date: Wednesday, June 28th, 2017
Time: 10:45 AM
Number: 36003
Abstract ID:433
Candidate for Awards:None

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