Fire-mediated effects of shrubs, lichens and herbs on the demography of Hypericum cumulicola in patchy Florida scrub

Abstract

Understanding the effect of disturbance and interspecific interactions on population dynamics and availability of suitable habitats for colonization and growth is critical for conservation and management of endangered species. Hypericum cumulicola is a narrowly endemic, small perennial herb virtually restricted to open areas of well-drained white sand in Florida rosemary scrub, a naturally patchy community that burns about every 20-80 years. Over 1 year (September 1994 to September 1995) we evaluated variation in survival, growth and fecundity among 1214 individuals in 14 rosemary scrub patches of different sizes (0.09-1.85 ha) and fire histories (2, 8-10, and >20 years since the last fire). Fire kills aboveground individuals of H. cumulicola, but new individuals were present a year after fire. Recruitment decreased in patches more than a decade post-fire. Survival, annual height growth rate, and fecundity (number of flowers and fruits) were higher in recently burned patches. Scrub patch size did not affect these demographic variables. Survival was positively associated with the presence of conspecifics and negatively related to proximity to the dominant shrub Florida rosemary (Ceratiola ericoides), prior reproductive output, and ground lichen cover. Since H. cumulicola and other herbaceous species in the rosemary scrub depend on sporadic fires to decrease interference of shrubs and ground lichens, its persistence may be threatened by fire suppression.

Effects of population size and isolation on heterosis, mean fitness, and inbreeding depression in a perennial plant

“…Within a patch of rosemary scrub, H. cumulicola is a specialist of open sandy gaps that support few to many hundreds of individuals. The gaps are maintained by periodic fire (Quintana‐Ascencio & Morales‐Hernandez, 1997; Quintana‐Ascencio & Menges, 2000; Quintana‐Ascencio et al. , 2003), which may kill adults of this species, but gaps can be quickly recolonized from a persistent seed bank (P. F. Quintana‐Ascencio, unpublished).…”

A Fire‐Explicit Population Viability Analysis of Hypericum cumulicola in Florida Rosemary Scrub

“…H. cumulicola is self‐compatible but requires the services of pollinators to set seed ( Evans et al, in press). Fire kills aboveground individuals ( Menges & Kohfeldt 1995; Quintana‐Ascencio & Morales‐Hernández 1997 ), but seeds in the soil survive fire and form long‐lived seed banks ( Quintana‐Ascencio et al 1998 ). Fire suppression and alteration of fire regimes constitute threats to this species because of its dependence on fire to release local populations from competitive exclusion (Quintana‐Ascencio & Morales Hernández 1997; Quintana‐Ascencio & Menges 2000 ).…”

Allelopathic effects and root distribution of Ceratiola ericoides (Empetraceae) on seven rosemary scrub species

“…d From Menges and Salzman (1992), Menges and Kohfeldt (1995), Young and Menges (1999), Menges and Kimmich (1996), Quintana-Ascencio and Morales-Hernandez (1997), and E. S. Menges, unpublished data. e From Menges and Kohfeldt (1995). 1995; Menges and Kimmich, 1996;Quintana-Ascencio and Morales-Hernandez, 1997). Specifically, we ask the following questions.…”

“…Many of these species favor microhabitats in gaps, at a distance from Florida rosemary shrubs (Menges and Kimmich, 1996;Quintana-Ascencio and Morales-Hernandez, 1997). As rosemary scrub patches age and Florida rosemary canopy increases, gaps will persist (Hawkes and Menges, 1996), but populations of some herbaceous species within these gaps will often decline (Menges and Kimmich, 1996;Quintana-Ascencio and Morales-Hernandez, 1997).…”