Greater Everglades Ecosystem Research Articles

Ecological function maintained despite mesomammal declines

Mid-sized mammals (i.e., mesomammals) fulfill important ecological roles, serving as essential scavengers, predators, pollinators, and seed dispersers in the ecosystems they inhabit. Consequently, declines in mesomammal populations have the potential to alter ecological processes and fundamentally change ecosystems. However, ecosystems characterized by high functional redundancy, where multiple species can fulfil similar ecological roles, may be less impacted by the loss of mesomammals and other vertebrates. The Greater Everglades Ecosystem in southern Florida is a historically biodiverse region that has recently been impacted by multiple anthropogenic threats, most notably the introduction of the Burmese python (Python molurus bivittatus). Since pythons became established, mesomammal populations have become greatly reduced. To assess whether these declines in mesomammals have affected two critical ecosystem functions—scavenging and frugivory—we conducted experiments in areas where mesomammals were present and absent. We did not observe significant differences in scavenging or frugivory efficiency in areas with and without mesomammals, but we did observe significant differences in the communities responsible for scavenging and frugivory. Despite the observed evidence of redundancy, the changes in community composition could potentially lead to indirect consequences on processes like seed dispersal and disease dynamics within this ecosystem, emphasizing the need for further study.

Wetland restoration enhances habitat for an endangered bat, Eumops floridanus

Restoring lost or degraded wetlands is a major challenge in contemporary conservation. Understanding how wetland restoration and changes in hydrology affect wildlife is increasingly urgent for endangered species conservation. This is especially pertinent for the endangered Florida bonneted bat (Eumops floridanus), whose range is almost entirely contained within one of the world's most iconic wetland systems, the Greater Everglades Ecosystem. We investigated how E. floridanus may respond to future hydrological and vegetation changes associated with current and planned Everglades hydrologic restoration efforts. We conducted acoustic surveys at 194 random points stratified across a restoration gradient (no hydrologic restoration, partial hydrologic restoration, full hydrologic restoration, and reference). Using generalized linear mixed models, we determined the most important predictors explaining variation in bat activity and foraging likelihood. Positive associations between bat activity and several hydrologic variables expected to increase with restoration (hydroperiod, water depth, distance to canals, and extent of freshwater forested wetlands, ecologically intact reference areas, and zones with full hydrological restoration) suggest that foraging habitat for this species will likely benefit from hydrologic restoration both in the near term (immediate increases in hydroperiod and water depth) and in the longer term (as freshwater forested wetlands expand). Our results inform immediate management decisions for this species and suggest the benefits of restoration for wildlife adapted to historically longer hydroperiods and greater water depths, which are anticipated to increase with the gradual return of natural hydrological regimes.

Ecological implications of allometric relationships in American alligators (Alligator mississippiensis)

Morphometric allometry, the effect of size on morphological variation, has been of great interest for evolutionary biologist and is currently used in fields such as wildlife ecology to inform management and conservation. We assessed American alligator (Alligator mississippiensis) morphological static allometry across the Greater Everglades ecosystem in South Florida, United States using a robust dataset (~ 22 years) and investigated effects of sex, habitat, and sampling area on morphological relationships. Regression models showed very strong evidence of a linear relationship between variables explaining equal to or above 92% of the variation in the data. Most trait–size relationships (8 out of 11 assessed) showed hyperallometry (positive allometry) with slope deviations from isometry between 0.1 and 0.2 units while the other three relationships were isometric. Sampling area, type of habitat, and in a lesser extent sex influenced allometric coefficients (slope and intercept) across several relationships, likely as result of differing landscapes and ecosystem dynamic alterations and sexual dimorphism. We discuss our findings in terms of the biology of the species as well as the usefulness of our results in the context of ecosystem restoration and conservation of the species. Finally, we provide recommendations when using trait–length relationships to infer population nutritional—health condition and demographics.

Burmese pythons in Florida: A synthesis of biology, impacts, and management tools

Burmese pythons (Python molurus bivittatus) are native to southeastern Asia, however, there is an established invasive population inhabiting much of southern Florida throughout the Greater Everglades Ecosystem. Pythons have severely impacted native species and ecosystems in Florida and represent one of the most intractable invasive-species management issues across the globe. The difficulty stems from a unique combination of inaccessible habitat and the cryptic and resilient nature of pythons that thrive in the subtropical environment of southern Florida, rendering them extremely challenging to detect. Here we provide a comprehensive review and synthesis of the science relevant to managing invasive Burmese pythons. We describe existing control tools and review challenges to productive research, identifying key knowledge gaps that would improve future research and decision making for python control.

Size distribution and reproductive phenology of the invasive Burmese python (Python molurus bivittatus) in the Greater Everglades Ecosystem, Florida, USA

The design of successful invasive species control programs is often hindered by the absence of basic demographic data on the targeted population. Establishment of invasive Burmese pythons (Python molurus bivittatus) in the Greater Everglades Ecosystem, Florida USA has led to local precipitous declines (> 90%) of mesomammal populations and is also a major threat to native populations of reptiles and birds. Efforts to control this species are ongoing but are hampered by the lack of access to and information on the expected biological patterns of pythons in southern Florida. We present data from more than 4,000 wild Burmese pythons that were removed in southern Florida over 26 years (1995–2021), the most robust dataset representing this invasive population to date. We used these data to characterize Burmese python size distribution, size at maturity, clutch size, and seasonal demographic and reproductive trends. We broadened the previously described size ranges by sex and, based on our newly defined size-stage classes, showed that males are smaller than females at sexual maturity, confirmed a positive correlation between maternal body size and potential clutch size, and developed predictive equations to facilitate demographic predictions. We also refined the annual breeding season (approx.100 days December into March), oviposition timing (May), and hatchling emergence and dispersal period (July through October) using correlations of capture morphometrics with observations of seasonal gonadal recrudescence (resurgence) and regression. Determination of reproductive output and timing can inform population models and help managers arrest population growth by targeting key aspects of python life history. These results define characteristics of the species in Florida and provide an enhanced understanding of the ecology and reproductive biology of Burmese pythons in their invasive Everglades range.

Face-off: Novel depredation and nest defense behaviors between an invasive and a native predator in the Greater Everglades Ecosystem, Florida, USA.

We describe several photo‐documented novel interactions between intraguild predators in southern Florida—the native bobcat (Lynx rufus) and the invasive Burmese python (Python bivittatus). Over several days we documented a bobcat's depredation of an unguarded python nest and subsequent python nest defense behavior following the return of both animals to the nest. This is the first documentation of any animal in Florida preying on python eggs, and the first evidence or description of such antagonistic interactions at a python nest.

Predicting effects of water management on breeding abundance of three wading bird species

AbstractWetland conservation often involves creating hydrological regimes that maximize habitat and resources for wildlife. In the greater Everglades ecosystem in Florida, USA, where wading birds are food‐limited in some years, models predicting the influence of hydropatterns on foraging habitat availability are used to guide the management of water levels for wading bird nesting populations. These models are useful but do not consider that nesting wading birds are central place foragers, and thus resource availability is a colony‐level measure. We examined long‐term nest abundance patterns of the great egret (Ardea alba), snowy egret (Egretta thula), and white ibis (Eudocimus albus) to determine effects of hydropatterns on wading bird nest abundance in a 400‐km2 littoral marsh in Lake Okeechobee, Florida. We developed 2 sets of statistical models for each species: 1 examining variation in nest abundance (1977–1992, 2006–2019) and 1 predicting colony‐level nest abundance (2006–2019). Models of nest abundance predicted that great egret nesting will peak when March–April lake stage is 4.3–4.5 m, coinciding with the peak in area of available foraging habitat. Neither recession rate nor stage explained total snowy egret or white ibis nest abundance, though snowy egret nest abundance has increased since the 1990s, when the water management schedule favored higher lake stages for longer duration. For all species, colony‐level models predicted that nesting increased with increased habitat availability, faster water‐level recession rates, and greater number of days dry in the previous 2 years at nest sites. When applied to simulated hydrological data representing changes to water‐level regulations in Lake Okeechobee, our models predicted that management regimes allowing extreme flooding (stage > 5.18 m) in <220 days per 5.0 years and Carolina willow (Salix caroliniana) recruitment (stage < 3.9 m) >3.0 years per 5.0 years resulted in the highest nest abundance for snowy egret and white ibis. Snowy egret and white ibis nesting decreased by 575 nests/year and 465 nests/year, respectively, when regulation schedules increased the management envelope by 0.46 m, whereas great egret nest abundance increased modestly (149 nests/year). Operational rules that allow intermediate drought disturbance in dry years and prioritize increased habitat availability at short‐hydroperiod colonies in wet years should result in overall benefits to the wading bird community at Lake Okeechobee.

Clutch may predict growth of hatchling Burmese pythons better than food availability or sex.

ABSTRACTIdentifying which environmental and genetic factors affect growth pattern phenotypes can help biologists predict how organisms distribute finite energy resources in response to varying environmental conditions and physiological states. This information may be useful for monitoring and managing populations of cryptic, endangered, and invasive species. Consequently, we assessed the effects of food availability, clutch, and sex on the growth of invasive Burmese pythons (Python bivittatus Kuhl) from the Greater Everglades Ecosystem in Florida, USA. Though little is known from the wild, Burmese pythons have been physiological model organisms for decades, with most experimental research sourcing individuals from the pet trade. Here, we used 60 hatchlings collected as eggs from the nests of two wild pythons, assigned them to High or Low feeding treatments, and monitored growth and meal consumption for 12 weeks, a period when pythons are thought to grow very rapidly. None of the 30 hatchlings that were offered food prior to their fourth week post-hatching consumed it, presumably because they were relying on internal yolk stores. Although only two clutches were used in the experiment, we found that nearly all phenotypic variation was explained by clutch rather than feeding treatment or sex. Hatchlings from clutch 1 (C1) grew faster and were longer, heavier, in better body condition, ate more frequently, and were bolder than hatchlings from clutch 2 (C2), regardless of food availability. On average, C1 and C2 hatchling snout-vent length (SVL) and weight grew 0.15 cm d−1 and 0.10 cm d−1, and 0.20 g d−1 and 0.03 g d−1, respectively. Additional research may be warranted to determine whether these effects remain with larger clutch sample sizes and to identify the underlying mechanisms and fitness implications of this variation to help inform risk assessments and management. This article has an associated First Person interview with the first author of the paper.

Spatial ecology of invasive Burmese pythons in southwestern Florida

AbstractUnderstanding the spatial ecology of an invasive species is critical for designing effective control programs. Determining and quantifying home range estimates and habitat associations can streamline targeted removal efforts for wide‐ranging, cryptic animals. The Burmese python (Python bivittatus) is a large‐bodied constrictor snake with an established and expanding invasive population in southern Florida. This apex predator has severely impacted native wildlife across the Greater Everglades ecosystem. However, limited ecological information exists on this invasive species at the landscape level. Here, we present results from a study using radiotelemetry to quantify movements and habitat use patterns of 25 adult Burmese pythons in southwestern Florida, USA, for average periods of 814 d (range: 288–1809). Our objective was to quantify home range size, movement rates, and second‐ and third‐order habitat selection. Mean annual home range size was 7.5 km2 ± 2.9 km2 (95% kernel density estimate), and pythons moved at a maximum mean daily rate of 0.52 km/d. Burmese pythons selected agriculture, freshwater wetland, saline wetland, and upland land cover classes but avoided open water and urban land cover classes. Nest site selection was highest for pythons at an elevation of 1.7 m with nesting hotspots concentrated on the borders of urban and agricultural areas or in sandy forested upland habitats. A broader understanding of the spatial utilization of Burmese pythons will enhance the utility of emerging control strategies across their invaded range.

A dry future for the Everglades favors invasive herpetofauna

The Greater Everglades Ecosystem is a globally important ecoregion, home to 68 threatened or endangered species and the largest designated wilderness area in the Eastern United States. Anthropogenic manipulations of the natural hydrology have led to widespread degradation of this ecosystem and monitored population declines across multiple taxa. Simultaneous introductions of hundreds of non-native species into South Florida and their subsequent invasion into the Everglades has further impacted native Everglades communities. Predictions for future climate change suggest that the Everglades is headed towards a drier future, making it crucial to understand how changes in hydrological regimes will impact both native and non-native fauna. Our study combines the results of a landscape-scale experimental manipulation conducted to assess the impact of differing hydrological regimes at the Loxahatchee Impoundment Landscape Assessment between 2018 and 2020 with a community composition analysis of data collected across multiple habitat types throughout Everglades National Park between 2000 and 2002. Both datasets used a variety of survey methods to extensively characterize the amphibian and reptile amphibian assemblage across habitat types and hydrological regimes. An NMDS analysis indicated that variation in hydrology is the primary axis structuring reptile and amphibian habitat usage across the Everglades, with non-native species more likely to be indicators of drier habitat types. This result concurred with those from the landscape-scale manipulation, in which non-native species were significantly favored by drier hydrological conditions. Taken together, these results suggest that a drier future within the Greater Everglades Ecosystem may facilitate further spread of South Florida’s diverse non-native amphibian and reptile assemblage.

Small mammal responses to wetland restoration in the Greater Everglades ecosystem

Wetlands have experienced dramatic losses in extent around the world, disrupting ecosystem function, habitat, and biodiversity. In Florida's Greater Everglades, a massive restoration effort costing billions of dollars and spanning multiple decades is underway. As Everglades restoration is implemented in incremental projects, scientists and planners monitor the outcomes of projects. In this study, we evaluated the progress of a restoration project in the southwestern Everglades. We aimed to determine whether the presence and density of small mammals differed between areas with the hydrologic restoration of the ecosystem and areas without restoration. Our three focal species were: marsh rice rat (Oryzomys palustris), hispid cotton rat (Sigmodon hispidus), and cotton mouse (Peromyscus gossypinus). Using spatially explicit capture‐recapture models, we found greater densities of cotton mouse in restored habitat and lower densities of hispid cotton rat in sites with higher water levels. In addition, we found an increase in the presence of the marsh rice rat in restored areas compared to unrestored, but captures were too low to reliably assess significance. Our study provides evidence that ongoing restoration in the southwestern Everglades is already impacting the small mammal community.

Economic valuation of the ecological response to hydrologic restoration in the Greater Everglades ecosystem

Economic analyses incorporating ecological and hydrological benefits are useful in guiding and justifying large and complex environmental restoration programs. The Greater Everglades region in Florida, USA is a large area of freshwater and estuarine wetlands adjacent to dense human populations undergoing an extensive restoration effort. Six Everglades restoration scenarios were modeled involving combinations of decompartmentalization (removal of canals and levees), extent of seepage control, and volume of water storage (296–3084 million m3)—all core components of the Comprehensive Everglades Restoration Plan. Under these scenarios, we simulated changes in ecological indicators across the Everglades, including Everglade snail kites and apple snails, wading birds, American alligators, and spotted seatrout. We also evaluated reductions of harmful discharges from Lake Okeechobee to the St. Lucie and Caloosahatchee estuaries in each scenario. Results were structured as options in a willingness-to-pay survey to aid in quantifying the benefits of restoration. Overall, we found Everglades restoration would increase ecosystem service benefits by $1.18 billion to $1.53 billion annually. A moderate amount of water storage improved ecosystem service benefits for Everglade snail kites and apple snails, American alligators, and wading birds, but additional storage led to equal or reduced benefits. For discharge reduction and spotted seatrout, ecosystem service benefits increased in proportion to the volume of water storage. Moderate water storage (1850 million m3) led to the greatest total ecosystem service benefits for the entire region, while the highest water storage volume led to the greatest benefits for specific Everglades regions like Florida Bay, St. Lucie, and Caloosahatchee estuaries. These results demonstrate the importance of economic valuation in estimating the potential ecosystem service benefits from large-scale environmental restoration and as a decision-support tool for prioritizing projects.

Life-history traits moderate the susceptibility of native mammals to an invasive predator

The invasive Burmese python (Python molurus bivittatus) is causing declines in the numbers and diversity of native mammals in the Greater Everglades Ecosystem (GEE). However, limited evidence suggests that some species may be less susceptible to pythons than others. This difference in susceptibility may be a function of different life-history traits. We analysed incidence data with a multi-species hierarchical occupancy model to evaluate the influence of pythons on native mammals and examine the association between python’s influence on species occurrence and life-history traits. We also used our traits-based model to predict the effects of pythons on occupancy probabilities of five mammalian species of conservation or management concern known to occur in the GEE but not detected in our study. Ten of 18 observed mammals showed significant negative effects from pythons, while one responded positively. We found that three of the six species traits evaluated (mass, fecundity, and habitat breadth) moderated the negative effects of pythons on mammal occurrence and were, thus, useful for predicting species responses. Our results suggest larger, fecund and/or species with wide habitat breadths were less susceptible to increasing relative densities of pythons. Our results also suggest a positive and neutral associations between rodents and relative python density, likely due to wide habitat breadths, high fecundity rates, and the reduction of mammalian predators in areas with higher relative python densities. These trait relationships predicted a negative response of all five unobserved species of management concern included in our analysis. Our study provides a broader understanding of wildlife community vulnerability to invasive predators and demonstrates how trait-based models can be used to elucidate generalizable patterns and generate predictions for rare and/or undetected species.

Scrutinizing biological control survey data from the native range – the phylogeny and Lygodium fern host associations of Musotiminae moths

Lygodium microphyllum is considered one of the most damaging environmental weeds in Florida. Despite substantial efforts to control this fern, it continues to spread rapidly through the Greater Everglades ecosystem and other regions of Florida. Biological control is considered a critical component of the management strategy to control this weed, and foreign exploration for natural enemies is ongoing. A number of crambid moths from the subfamily Musotiminae are considered the most promising of the potential biological control agents found to date, because they are relatively abundant on Lygodium and apparently host-specific. We amplified three genes (COI, 18S rRNA and 28S rRNA) to assess the phylogenetic relationships among these moths in relation to geography. Limited genetic structuring was typical within each moth species, and no obvious signals of unrecognised host-specific cryptic species were detected, though further investigation is required, particularly for Eugauria albidentata. Our results emphasize the value of complementing initial field surveys with molecular screening, as such an approach provides valuable information on the biogeographic distribution, genetic structuring, and field host range of potential biological control agents.

Efficacy of eDNA as an early detection indicator for Burmese pythons in the ARM Loxahatchee National Wildlife Refuge in the greater Everglades ecosystem

Environmental DNA (eDNA) detection of invasive species can be used to inform management decisions by delimiting occupied ranges and estimating detection probabilities. Environmental DNA is shed into the environment through skin cells and bodily fluids and can be detected in water samples collected from lakes, rivers, and swamps. In south Florida, USA, invasive Burmese pythons (Python bivittatus) occupy much of the Greater Everglades in mostly inaccessible habitat and are credited with causing severe declines in populations of native species. Detection of Burmese pythons by traditional methods, including trapping and visual searching, has been largely ineffective, making eDNA a superior method to identify invaded areas. We adapted a quantitative PCR eDNA assay for use in droplet digital PCR, a state-of-the-art method that improves the precision and accuracy of eDNA detection and quantification. From August 2014 to October 2016, locations in and around Arthur R. Marshall Loxahatchee National Wildlife Refuge in southeast Florida were surveyed for Burmese python eDNA. Positive eDNA detections were made in each of the five sampling events, assessing a total of 399 samples, with moderate-to-high occurrence (ψ = 58–91%) and moderate detection (p = 38–70%) probabilities, potentially reduced by a high presence of PCR-inhibiting compounds in the water. The high occurrence rates and geographic distribution of the positive samples within Loxahatchee suggests a steady release of python eDNA from resident Burmese pythons and reduces support for transport of eDNA by boats or flowing water from the north. The first confirmed sighting of a Burmese python in the Refuge occurred in September 2016 after eDNA testing had indicated the presence of pythons. While the established population boundary is thought to be south of Loxahatchee, the eDNA detections indicate a northern range limit at, or north of, the refuge on the eastern side of the Florida peninsula. Our study demonstrates the utility of eDNA for determining more accurate range limits and expansion information for Burmese pythons, and provides a means for assessing control efforts.

Recreational Fishing in Florida Bay: Economic Significance and Angler Perspectives

Florida Bay is a large, shallow, subtropical estuary located off the southern tip of the Florida peninsula and north of the Florida Keys, and is mostly contained within the bounds of Everglades National Park. Its unique ecological characteristics and location near densely populated urban areas make Florida Bay a popular tourist destination for recreational fishing. A survey of recreational anglers and guides was conducted to estimate the economic significance of recreational fishing in the Bay. Results indicate that recreational fishing on Florida Bay contributed $439 million in economic activity to the local economy in the year the study was conducted. Further, anglers from outside the region made up a disproportionate share of the economic contribution. Anglers were also queried through the survey about their opinions of the current status of the Bay. Most respondents indicated that they perceived that the quality of fish populations and habitat was declining, and that they fished the Bay less frequently than in the past. The importance of the results to restoration efforts targeting the Bay and the greater Everglades ecosystem is discussed.

Critically imperiled forest fragment supports bat diversity and activity within a subtropical grassland

Global biodiversity patterns are shaped by landscape structure and seasonality. Spatio-temporal patterns in bat assemblages are not well studied in grassland biomes but forest patches may provide important habitat for bats within these open grasslands. In the Greater Everglades Ecosystem (GEE), small fragments of diverse, critically imperiled pine rockland remain amidst a vast expanse of seasonally flooded grasslands (marl prairies). We used acoustic surveys to investigate the use of pine rocklands and marl prairies by bats across 2 distinct seasons (dry-cool and wet-warm). We detected higher mean bat activity in pine rocklands than marl prairies in the dry-cool season and higher bat species richness in pine rocklands in both seasons. Four of the 9 species of bats exhibited higher mean activity in pine rocklands than marl prairies and higher activity in the wet-warm season. The greater structural complexity of pine rocklands relative to marl prairies may be attractive to bats for roosting, foraging, and protective cover. Our finding of an interactive effect between vegetation community and season on bat activity suggests that pine rocklands may be more attractive to bats in the dry-cool season. This may be due to microclimate moderation, which likely leads to higher insect abundance for foraging bats. Pine rocklands in the GEE clearly provide ecological benefits that help support local biodiversity. These forest patches are important landscape elements for bats in grassland communities, where available roosts, prey, and protective cover may be limited.

Urbanization may limit impacts of an invasive predator on native mammal diversity

AbstractAimOur understanding of the effects of invasive species on faunal diversity is limited in part because invasions often occur in modified landscapes where other drivers of community diversity can exacerbate or reduce the net impacts of an invader. Furthermore, rigorous assessments of the effects of invasive species on native communities that account for variation in sampling, species‐specific detection and occurrence of rare species are lacking. Invasive Burmese pythons (Python molurus bivittatus) may be causing declines in medium‐ to large‐sized mammals throughout the Greater Everglades Ecosystem (GEE); however, other factors such as urbanization, habitat changes and drastic alteration in water flow may also be influential in structuring mammal communities. The aim of this study was to gain an understanding of how mammal communities simultaneously facing invasive predators and intensively human‐altered landscapes are influenced by these drivers and their interactions.LocationFlorida, USA.MethodsWe used data from trail cameras and scat searches with a hierarchical community model that accounts for undetected species to determine the relative influence of introduced Burmese pythons, urbanization, local hydrology, habitat types and interactive effects between pythons and urbanization on mammal species occurrence, site‐level species richness, and turnover.ResultsPython density had significant negative effects on all species except coyotes. Despite these negative effects, occurrence of some generalist species increased significantly near urban areas. At the community level, pythons had the greatest impact on species richness, while turnover was greatest along the urbanization gradient where communities were increasingly similar as distance to urbanization decreased.Main conclusionsWe found evidence for an antagonistic interaction between pythons and urbanization where the impacts of pythons were reduced near urban development. Python‐induced changes to mammal communities may be mediated near urban development, but elsewhere in the GEE, pythons are likely causing a fundamental restructuring of the food web, declines in ecosystem function, and creating complex and unpredictable cascading effects.

Spatial metrics for detecting ecosystem degradation in the ridge-slough patterned landscape

Indicators of landscape condition should be selected based on their sensitivity to environmental changes and their capacity to provide early warning detection of those changes. We assessed the performance of a suite of spatial-pattern metrics selected to quantify the condition of the ridge-slough landscape in the Everglades (South Florida, USA). Spatial pattern metrics (n=14) that describe landscape composition, geometry and hydrologic connectivity were enumerated from vegetation maps of twenty-five 2×2km primary sampling units (PSUs) that span a gradient of hydrologic and ecological condition across the greater Everglades ecosystem. Metrics were assessed in comparison with field measurements from each PSU of landscape condition obtained from regional surveys of soil elevation, which have previously been shown to capture dramatic differences between conserved and degraded locations. Elevation-based measures of landscape condition included soil elevation bi-modality (BISE), a binary measure of landscape condition, and also the standard deviation of soil elevation (SDSE), a continuous measure of condition. Metric performance was assessed based on the strength (sensitivity) and shape (leading vs. lagging) of the relationship between spatial pattern metrics and these elevation-based measures. We observed significant logistic regression slopes with BISE for only 4 metrics (slough width, ridge density, directional connectivity index – DCI, and least flow cost – LFC). More significant relationships (n=8 metrics) were observed with SDSE, with the strongest associations for slough density, mean ridge width, and the average length of straight flow, as well as for a suite of hydrologic connectivity metrics (DCI, LFC and landscape discharge competence – LDC). Leading vs. lagging performance, inferred from the curvature of the association obtained from the exponent of fitted power functions, suggest that only DCI was a leading metric of the loss of soil elevation variation; most metrics were indeterminate, though some were clearly lagging. Our findings support the contention that soil elevation changes from altered peat accretion dynamics precede changes in landscape pattern, and offer insights that will enable efficient monitoring of the ridge-slough landscape as part of the ongoing Everglades restoration effort.

Ruppia maritima L. seed bank viability at the Everglades-Florida Bay ecotone

Ruppia maritima L. is a cosmopolitan habitat-forming seagrass species that historically dominated at the Everglades-Florida Bay ecotone in the Greater Everglades Ecosystem. Currently, however, this species exhibits a patchy and ephemeral distribution which results in a degraded habitat. Thus, an important goal in Everglades’ habitat restoration is to increase R. maritima abundance in the southern Everglades estuaries. We tested the hypothesis that a lack of seed bank viability may be limiting R. maritima recruitment potential. We surveyed the seed bank along the ecotone across western, central and eastern Florida Bay transects (28 sites); a large reproductive event was also captured at a western site. Seed densities were quantified and seeds characterized into intact (viable and nonviable), germinated and decomposing. Sediment nutrients were also determined from cores at each site. Transect data indicated low seed densities (150–1783m−2) and few viable seeds (0–160m−2) with higher total densities at western and central (643–1783m−2) compared to eastern sites (150–327m−2). In contrast, a meadow undergoing sexual reproduction had high total (25,398m−2) and viable seeds (3556m−2). Total and germinated seeds were also positively predicted by sediment P. While the Everglades ecotone is generally depauperate with respect to R. maritima seeds, an “opportunistic” recruitment strategy sustains it within the community. To restore this species as a highly productive habitat, restoration should focus on R. maritima life history development to seed set, and promoting the development of large reproductive meadows characterized by high seeds densities and a high proportion of viable embryos.