Coreopsis rosea

Coreopsis rosea is a perennial forb of the Atlantic Coastal Plain region, found predominantly from eastern Massachusetts and Rhode Island south through southeastern New York, New Jersey, Delaware, and eastern Maryland, with disjunct occurrences found in Nova Scotia, South Carolina, and Georgia. Approximately 98 occurrences are believed extant, the majority of which are found in Massachusetts. Coreopsis rosea is present at nearly all coastal plain ponds in Massachusetts, with plants usually very abundant where habitat is intact, often persisting in small clumps at disturbed and degraded ponds. This species seems better able to persist at very degraded and disturbed coastal plain ponds than other globally rare coastal plain pond associates. Many occurrences contain hundreds or thousands of plants, and the total population may exceed 100,000 plants. Threats to this species are considerable and include habitat destruction from development, soil disturbance due to heavy recreational use particularly by all-terrain vehicles, alteration of the naturally fluctuating hydrological regime due to municipal drawdown or intentional stabilization of lake levels, eutrophication, competition from invasive species, and fire suppression.

Coreopsis rosea is found in eastern North America and is primarily a species of the Atlantic Coastal Plain region, occurring from eastern Massachusetts and Rhode Island south through New York, New Jersey, Delaware, and eastern Maryland in the United States (FNA 2006, Weakley and the Southeastern Flora Team 2024). One occurrence was recorded in eastern Pennsylvania, but it is now believed to be extirpated (PNHP 1986). Disjunct occurrences are also found in southwestern Nova Scotia, Canada, and in South Carolina and Georgia (COSEWIC 2012). The Flora of North America Editorial Committee (2006) states that the "occurrence of C. rosea in South Carolina may represent a human-mediated disjunction; the collection came from a 'lime sink' near a trailer park close to a freeway." However, the South Carolina Natural Heritage Program has mapped several occurrences in the state and considers the species to be native (NatureServe 2024). Range extent was estimated using herbarium specimens and NatureServe Network occurrence data collected between 1993 and 2024 (GBIF 2024, NatureServe 2024, SEINet 2024).

There are an estimated 98 extant, non-historical occurrences in the United States tracked by the NatureServe Network, with the majority occurring in Massachusetts (48) and New York (29) (NatureServe 2024). Using NatureServe's population separation guidelines, there are an estimated six extant occurrences in Canada, and two historical occurrences which are considered extirpated (COSEWIC 2012, NatureServe 2024).

There are a number of significant threats to this species (Keddy and Wisheu 1989, Wisheu and Keddy 1989, Schuyler 1990, J. Garrett, pers. comm., 2009, S. Young, pers. comm., 2009). Habitat destruction caused by dredging and filling wetland habitats for development is a threat in many parts of the range, and it is considered a primary threat to populations in Massachusetts (MDFW 2015). Soil disturbance due to heavy recreational use, particularly disturbance by all-terrain vehicles, is also an issue at many sites as the gently sloping gravel shorelines that this species prefers are conducive to all-terrain vehicle use (NYNHP 2006, COSEWIC 2012). Alteration of the naturally fluctuating hydrological regime, with underlying causes such as excessive municipal drawdown of the water table or intentional stabilization of lake levels, is leading to decline of some populations as more competitive species such as pitch pine are consequently able to establish and eventually dominate Coreopsis rosea habitat (Craine and Orians 2004). Eutrophication of oligotrophic lakes is also an issue, and it is considered to be the most significant threat to Canadian populations (COSEWIC 2012). Nutrients from sources such as run-off containing fertilizer and pet waste, water contamination from septic systems, and atmospheric deposition enter lake systems and tend to favor more competitive species over species such as C. rosea that are adapted to infertile soils. Invasive plants that occupy the same emergent habitat zone as C. rosea are also a threat at some sites, and Phragmites spp. can cause negative impacts (COSEWIC 2012, MDFW 2015, NYNHP 2024). Fire suppression is also potentially an issue at some sites, as it allows succession to proceed to the detriment of C. rosea (MDFW 2015). Finally, alterations to the hydrological regime that are predicted to occur as a result of climate change could be an issue for this species, as it is adapted to a fairly specific timing of water level flooding and receding.