Elizabeth A. Forys

Body Mass Patterns Predict Invasions and Extinctions in Transforming Landscapes

ABSTRACT Scale-specific patterns of resource distribution on landscapes entrain attributes of resident animal communities such that species body-mass distributions are organized into distinct aggregations. Species within each aggregation respond to resources over the same range of scale. This discontinuous pattern has predictive power: invasive species and extinct or declining species in landscapes subject to human transformation tend to be located at the edge of body-mass aggregations (P < 0.01), which may be transition zones between distinct ranges of scale. Location at scale breaks affords species great opportunity, but also potential crisis.

EFFECTS OF FIRE ANTS (HYMENOPTERA: FORMICIDAE) ON HATCHING TURTLES AND PREVALENCE OF FIRE ANTS ON SEA TURTLE NESTING BEACHES IN FLORIDA

Red imported fire ants (Solenopsis invicta Buren) have increasingly been observed in loggerhead (Caretta caretta L.) and green (Chelonia mydas L.) sea turtle nests in Florida, and in the nests of freshwater turtles. They may be attracted to the disturbance, mucous and moisture associated with turtle nesting and establish foraging tunnels into turtle nests shortly after egg-laying, thus increasing the vulnerability of hatchlings to fire ant predation. We conducted experiments on a freshwater turtle (Pseudemys nelsoni Carr) to determine the potential impacts of S. invicta on turtle hatchlings. Over 70% of hatchlings were killed by S. invicta during pipping or shortly after hatching. To determine the extent of S. invicta infestation of sea turtle nesting beaches, we sampled known nesting beaches throughout the state of Florida. Beach surveys indicated that S. invicta are present and often abundant on most beaches and dunes along the Florida coast.

Functional group change within and across scales following invasions and extinctions in the Everglades ecosystem

Cross-scale resilience theory predicts that the combination of functional diversity within scales and functional redundancy across scales is an important attribute of ecosystems because it helps these systems resist minor ecological disruptions and regenerate after major disturbances such as hurricanes and fire. Using the vertebrate fauna of south Florida, we quantified how the loss of native species and invasion by nonnatives may alter functional group richness within and across scales. We found that despite large changes in species composition due to potential extinctions and successful invasions by nonnative species, functional group richness will not change significantly within scales, there will not be any significant loss of overall redundancy of ecology function across scales, and overall body mass pattern will not undergo substantial change. However, the types of functions performed will change, and this change may have profound effects on not only the Everglades ecosystem but on the entire landscape of south Florida.

Influence of the proximity and amount of human development and roads on the occurrence of the red imported fire ant in the lower Florida Keys

We examined the influence of both the proximity and extent of human developments and paved roads on the presence of the predatory, non-indigenous, red imported fire ant (Solenopsis invicta). This species was inadvertently introduced into the United States at the port of Mobile, Alabama, around 1930 and rapidly spread to many southeastern states, including Florida. More recently, S. invicta colonized the Florida Keys, an area with a high proportion of rare and endemic vertebrate and invertebrate species. We placed bait transects in transitional salt-marsh, pineland, and hardwood hammocks on 13 of the lower Florida Keys and compared habitat type, the shortest distance of the bait transect to a development or road, and area of development and roads 50, 70, 100, and 150 m around each bait transect for areas with and without red imported fire ants. Red imported fire ants were detected on 21 of the 80 transects and were equally abundant in all habitat types. While all of the development and road variables differed significantly between bait transects with and without red imported fire ants, transects that were closest to roads and that had the largest amount of development within a 150 m radii had the highest probability of presence of red imported fire ants. Recovery efforts for endangered species in areas invaded by red imported fire ants should include analyses of the cumulative impacts of roads and developments in areas near protected lands.

The Impacts of Sprawl on Biodiversity: the Ant Fauna of the Lower Florida Keys

Sprawling development can affect species composition by increasing the rate of invasion by non-native species, and decreasing the persistence of native species. This paper briefly reviews the scientific literature on the impacts of sprawl on biological diversity, with specific emphasis on the influence of sprawl on non-native species richness. We then explore the relationship between sprawl and biodiversity using a data set of ant species collected from 46 habitat patches located in the increasingly suburbanized Florida Keys, USA. We quantified sprawl as the proximity of roads and amount of development surrounding a habitat patch. Using bait transects, we identified 24 native and 18 non-native species of ants. Neither the overall number of native species nor the number of rare native species were significantly affected by the amount of development or proximity to roads, however, the number of non-native species was significantly correlated with the amount of development. Surprisingly, the number of native species and rare native species was significantly positively correlated with the number of non-native species. Areas that supported many species of native ants also supported a diverse non-native ant fauna, and the species distribution was highly nested. Currently, the native ant fauna of the Florida Keys does not appear to be dramatically influenced by sprawl, however, if development increases, the number of non-native ants may increase, and many of these species have been documented as decreasing native ant diversity. If development plateaus, there is evidence that the native ant fauna could persist and could decrease non-native species richness through competition or predation.

POTENTIAL FIRE ANT (HYMENOPTERA: FORMICIDAE) IMPACT ON THE ENDANGERED SCHAUS SWALLOWTAIL (LEPIDOPTERA: PAPILIONIDAE)

The Schaus swallowtail, Papilio aristodemus ponceanus, historically occurred in tropical hardwood hammocks from South Miami to the upper Florida Keys and is currently listed as federally endangered. Much of the remaining hardwood hammock habitat is fragmented by roads and human development that may alter the microhabitat within the hammocks and increase the probability of invasion by non-native predators and competitors. One non-indigenous species that has recently invaded the Florida Keys, and that may impact the Schaus swallowtail is the red imported fire ant (Solenopsis invicta Buren). We estimated abundance of red imported fire ants in Schaus swallowtail habitat on Key Largo, and the decrease in red imported fire ants resulting from the application of chemical ant baits. In addition, we conducted laboratory experiments to determine how vulnerable swallowtail life stages are to red imported fire ant predation. We found red imported fire ants at 50% of transects in the hardwood hammock, up to 40 m from hammock edge. Chemical treatments were only partially effective in decreasing red imported fire ant abundance, and the effect was short-lived. All immature swallowtail life stages were vulnerable to predation by red imported fire ants. Habitat restoration that decreases red imported fire ant abundance may be the most cost-effective and long-term method of decreasing impacts from red imported fire ants.

Conservation Implications of Predation by Cuban Treefrogs (Osteopilus septentrionalis) on Native Hylids in Florida

Abstract The Cuban Treefrog, Osteopilus septentrionalis, is an invasive, non-native species whose range is rapidly expanding throughout Florida and may be a significant predator of native treefrogs. To investigate the attractiveness of various sized native Green Treefrogs as prey to Cuban Treefrogs, we conducted laboratory experiments where we offered very large Cuban Treefrogs the choice of arthropods (crickets), conspecifics, and Green Treefrogs. We found that all prey types were consumed by the very large Cuban Treefrogs over the course of the feeding trials. When given the choice of crickets or treefrogs as prey, more of the very large treefrogs ate just crickets and crickets were usually consumed before treefrogs. While not indicating a selection or preference for predation on other treefrogs, our trials did show that Cuban Treefrogs will eat both Green Treefrogs and conspecifics and could have a negative impact on native hylids by removing reproductively mature individuals from the population.

Roof-top Selection by Least Terns in Pinellas County, Florida

Abstract Primarily due to loss and disturbance of their open beach habitat, Least Tern (Sterna antillarum) nesting colonies often occur on flat or gently sloped gravel rooftops throughout the Southeastern United States. Currently, these rooftops are being converted to a new substrate, unsuitable for Least Tern nesting, because of changes in state building codes. The purpose of this study was to determine which rooftops Least Terns are currently selecting to help develop man-made structures for nesting and determine where these structures should be placed. From 1998-2003 in Pinellas County, Florida, all previously occupied Least Tern rooftops were surveyed to see if they had a colony and new colonies were located. In 2003, there were 36 rooftops with colonies and 34 unoccupied rooftops that had been previously occupied sometime from 1998-2002 but still had gravel rooftops. In addition, 36 gravel rooftops that had no record of supporting a Least Tern colony were randomly selected. At each building distance to any body of water, distance to a large body of water, distance to a higher building, distance to another colony, height of building, area of rooftop, number of taller trees/poles within 50 m and number of trees that touched the roof were measured. Backwards stepwise regression indicated that only distance to water significantly predicted if a rooftop was currently or never occupied. These results indicate that even relatively small, low structures, located near any body of water may be judged suitable by Least Terns and have the potential to help add to the species’ overall productivity.

Black Skimmers Feed When Light Levels are Low

Abstract. Previous studies documented that Black Skimmers, Rynchops niger; tend to forage at night but did not examine which environmental variables explain nocturnal foraging. Foraging frequency and environmental variables were studied at a large breeding colony of skimmers on an urbanized barrier island on the west coast of Florida, USA. To determine which variables influenced foraging, the number of skimmers departing to forage was counted for 120, one-hour periods through the day and night from 30 May–29 August, 2007. Using generalized linear models, factors were most associated with skimmers departing to forage were identified. These models included: light level, temperature, wind, wind direction, relative humidity, tide height, tide stage (incoming, outgoing, or slack) and status of the colony (mostly eggs, chicks, or fledglings). Light level was the only factor to significantly influence the amount of foraging (Wald = 9.40, d.f. = 1, p = 0.002). The relationship was negative, as light levels decreased, the number of birds departing to forage increased. The average proportion of the colony foraging per hour at night was 38.2% (SE = 4.6) and during the day the average proportion was 13.6% (SE = 4.0). The likely cause is that small, planktivorous fish come closer to the surface and shoreline at low light levels, allowing the skimmer to employ its unusual foraging technique of “skimming”.

Can Video Cameras Decrease Human Intrusion into a Closed Natural Area

ABSTRACT: Fort De Soto Park (Pinellas County, Florida) encompasses several barrier islands and is accessible to the public by road. Over 32 ha of beach are closed to the general public to allow birds to nest, loaf, and forage without human disturbance. The objective of this study was to use video monitoring of the closed area to determine when intrusions into the protected area occurred and to see if publicizing that the area is being video monitored increased compliance. We randomly chose 400 hours of daylight video from April through August, 2013, to determine the number of intruders. In the middle of the peak nesting season (July 2) we placed signs informing the public that they were being monitored. During the 349 hours where video quality was high, we had 27 hours where at least one intruder entered the area and 144 intruders total. Most of the intrusions were in the evening (1600–1900), during low tide, and on days with higher attendance. Signage communicating video recording of the bird sanctuary led to a strong negative impact on intrusion and was statistically significant (P = 0.01). The combination of using video cameras and signs informing the public about the video cameras was a highly effective method of reducing the number of people entering a closed portion of beach.