|MUKHERJEE, A - University Of Florida|
|WILLIAMS, D - Texas Christian University|
|CUDA, J - University Of Florida|
|PAL, S - University Of Florida|
|OVERHOLT, W - University Of Florida|
Submitted to: Biological Invasions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2011
Publication Date: 12/26/2011
Citation: Mukherjee, A., Williams, D.A., Wheeler, G.S., Cuda, J.P., Pal, S., Overholt, W.A. 2011. Brazilian peppertree (Schinus terebinthifolius) in Florida and South America: Evidence of a niche shift driven by hybridization. Biological Invasions. DOI: 10.1007/s10530-011-0168-7.
Interpretive Summary: Invasive weeds introduced in a new range can show large evolutionary change from strong selective forces in their new habitat. Some weed species have been introduced into their invasive range multiple times from various sources each contributing a distinct genetic makeup. This is the case for several weed species including Brazilian pepper. For this species, we know of two sources of introduction into Florida during the past 100 years. In Florida these two lines hybridized resulting in a different combination of genes than was originally introduced or than occur naturally in the area of origin of the plant. This paper maps the existing distribution of the original genetic strains of Brazilian pepper in its native range, Brazil, Argentina, and Paraguay and projects this and the hybrid’s range in Florida. We examined the climatic variables that might influence the native and invasive ranges of the weed and its potential to expand. We found that the plant’s invasive range was much different in terms of climatic conditions exploited compared with that in its native range. We found that the initial establishment of the weed in Florida was facilitated by similar conditions with the area of origin of the different introductions. Then with hybridization of the Florida strains and subsequent genetic diversity, these original introductions now exploit conditions beyond their original source with the potential to expand further.
Technical Abstract: Brazilian peppertree (Schinus terebinthifolius Raddi, Anacardiaceae) was introduced into Florida from South America in the 1800s and commercialized as an ornamental plant. Based on herbaria records and available literature, it began to escape cultivation and invade ruderal and natural habitats in the 1950s, and is now considered to be one of Florida's most widespread and damaging invasive plants. Historical records and genetic evidence indicate that two genetic lineages of Brazilian peppertree were established in Florida, one in Miami on the east coast and a second near Punta Gorda on the west coast. Since arriving, the distributions of these two types have greatly expanded, and they have extensively hybridized. Principal component analysis (PCA) and reciprocal niche fitting were used to test the equivalency of climatic niches of the Florida population with the climatic niches of the two South American chloroplast haplotype groups which established in Florida. Both approaches indicated a significant shift in niches between the parental populations in the native range and the invasive populations in Florida. The models, however, closely predicted the areas of initial establishment. We hypothesize that 1) Brazilian peppertree was able to gain an initial foothold in Florida due to niche similarity and cultivation and 2) the current dissimilarity in native and exotic niches is due to hybridization followed by rapid selection of genotypes adapted to Florida’s climate. In addition, to examine the potential consequence of the introduction of additional genetic diversity from the native range on invasion success, a niche model constructed with occurrences of all native genotypes was projected onto the continental United States. The result of this test indicated that under such an event, the potential invasive range would greatly expand to cover most of the southeastern USA. Our study suggests that multiple introductions from disjunct regions in the native range can facilitate invasion success.