Across its natural and invaded range, Melaleuca quinquenervia, an invasive tree from Australia and Papua New Guinea, produces oils correspondent to two distinct chemotypes. In Australia and Papua New Guinea, the two chemotypes separate geographically: Chemotype 1 occurs north of 25°S and both chemotypes occur south of 25°S. In south Florida, M. quinquenervia also occurs in two different habitats, dry and sandy soils in the west and wetter organic soils in the east. We investigated the effects of two biological control agents, the leaf feeding melaleuca snout weevil (Oxyops vitiosa), and the sap-sucking psyllid (Boreioglycaspis melaleucae) on both chemotypes in both types of habitats. We designed a common garden experiment to investigate the effects of herbivory and irrigation on M. quinquenervia growth between chemotypes. The E-nerolidol chemotype (chemotype 1) grew significantly faster than the viridiflorol chemotype (chemotype 2), regardless of herbivory exposure. Seed production in plants exposed to herbivory was reduced by more than 99% compared to plants with limited herbivory, regardless of chemotype. The final height of insecticide-treated plants was over double that of unsprayed plants and the final trunk biomass was five times greater. However, in our experiments the effects of insecticide on final plant height, final trunk biomass and final branch biomass were greater for viridiflorol than E-nerolidol, suggesting biological control may have a greater impact on viridiflorol trees. Increased irrigation did not affect herbivore numbers but did significantly increase final tree height and final branch weight, and for height this increase was greater for viridiflorol. While our research suggests biological control agents are effective against both chemotypes, they also show that impacts are affected by both chemotype and environment.

We used meta-analyses to examine the effects of different enemy taxa on insect prey populations as well as tri-trophic effects on their host plants. We also compared the effects of classical biocontrol, the use of biocontrol enemies for conservation biocontrol, and the use of naturally occurring enemies. Overall, there were strong negative effects of most enemy taxa on insect prey, but the effects of biocontrol enemies were significantly stronger than other naturally occurring enemies. There were differences in the strength of effects of enemy taxa with parasitoids, flying insect predators, ground insect predators other than ants, and spiders having stronger effects than ants or vertebrates such as birds, frogs, and bats. There were no significant differences between insect prey targets such as sucking insects, concealed feeders, leaf chewers, insect predators and detritivores. There were also no significant differences in the effects of enemies between insect prey of different origin, native or invasive, or host plant origin, native, invasive or introduced. However, the effects of enemies on their prey differed according to growth form of the prey host plant, with stronger effects of enemies or herbs and shrubs than on trees or grasses. There were no significant tri-trophic effects of enemies on the host plant morphometrics of their prey. There were also no significant difference in tri-trophic effects between biocontrol and non-biocontrol studies, enemy taxa, insect or plant origin, or plant growth form. However, the effects of enemies on prey were significantly negatively correlated with tri-trophic effects on plant morphometrics.

The semaphore cactus, Consolea corallicola, is an endangered tree cactus endemic to just two sites in the Florida Keys. Since the 1980s, it has been threatened by the arrival of an invasive cactus-eating moth, Cactoblastis cactorum, rot, and, more recently, by sea level rise. Between 1996 and 2017, we outplanted 641 propagated cacti at 10 different sites in the Lower Keys and 632 cacti at 19 sites in the Upper Keys in an effort to increase the population size. Some sites were actively managed, and others were not. Persistence of outplanted cacti was poor, with no long-term survival at 17 sites and low survival at most others. Cactoblastis accounted for 9% of deaths, but crown rot, caused by a pathogenic fungus, Fusarium oxysporum, was the leading cause of death, accounting for 77% of mortality. Elevated soil moisture likely contributes to the high levels of crown rot. Cages to protect cacti from Cactoblastis and fertilization to alleviate the effects of crown rot did not increase survival rates. Observed saltwater intrusion and storms killed an additional 6% and 4% of cacti, respectively. Taken together as a whole, increased water levels and soil moisture are likely responsible for 87% of the mortality of our outplanted cacti. Cacti at actively managed sites did not survive better than those that were not actively managed. Given the likelihood of increasing sea levels, storm strength, and storm frequency, future strategies to save this iconic plant from extinction should include more outplantings at higher elevation sites, with as many individuals as possible, on higher ground with more consideration given to the ecology and genetics of its close relatives.

We used meta-analyses to compare the effects of 44 single insect species used as biocontrol agents against invasive weeds with the effects of 51 species of non-biocontrol insects on native plants. The effects of biocontrol insects on plant morphometrics were stronger than those of non-biocontrol insects. Overall effects of both groups together were significantly different across plant growth forms with grasses, shrubs, and trees impacted more than vines and herbs. The effect of plant organ was also significant, with roots and fruits suffering the greatest impacts. Insect order had a significant effect: Hemiptera and Coleoptera showed strong effects and Diptera weak effects. Insect feeding guild had significant effects with leaf chewers, sap suckers, stem borers, and stem gallers having the strongest effects. There were no significant effects of study duration or latitude of location. For most categories of plant growth form, plant organ attacked, insect order and feeding guild, biocontrol insects had significantly stronger effects than their non-biocontrol counterparts. The effects of non-biocontrol insects grouped alone against native plants were not always a reliable guideline for how biocontrol insects grouped alone affected their target plants.

Invasive Melaleuca quinquenervia consists of two different chemotypes, E-viridiflorol and E-nerolidol that differentiate geographically in Florida: E-nerolidol dominates on the east coast and E-viridiflorol is more common on the west coast. Both chemotypes are susceptible to attack from three introduced herbivorous biological control insects from Australia: the leaf-feeding weevil, Oxyops vitiosa, the sap sucking psyllid, Boreioglycaspis melaleucae, and the stem-galling midge, Lophodiplosis trifida. Boreioglycaspis melaleucae were collected from areas in Queensland, Australia supporting only the E-viridiflorol chemotype whereas O. vitiosa and L. trifida were collected more broadly in Australia, in areas supporting both chemotypes. Here, we use reciprocal transplants of E-nerolidol and E-viridiflorol from Florida’s east and west coasts, and censuses of naturally occurring trees on both coasts, to determine if biological control agents (a) prefer one chemotype over another or (b) prefer one coastal site over another. Results showed that there was no chemotype preference of O. vitiosa or L. trifida, but we observed a significant preference for E-viridiflorol by B. melaleucae. There were also differences in herbivore densities between east and west coasts that were likely caused by different environmental conditions. We suggest both consideration of chemotype preference as well as impact of environment when selecting biological control agents for field releases.

AbstractThe Enemy Release Hypothesis (ERH) suggests that escape from natural enemies causes introduced plants to become invasive. We used meta-analysis to synthesize and investigate the strength of the ERH using both the biological control of invasive plants by individual introduced insects and the effects of individual native insect herbivores on native plants. Insects used in biological control studies, specified as both pre- and post-release, had significantly greater effects on invasive plants than native insects had on native plants, which supports the ERH. However, this effect was driven mostly by study outcomes from biocontrol releases, which had significantly greater effects on invasive plants than native insects had on native plants. Insects used in pre-release biocontrol studies did not have significantly stronger effects than native insects on native plants. This suggests that ERH may not be as common a cause of plant invasiveness as thought since, by that logic, release from natural enemies would cause any introduced plant species to become invasive. Among all studies, there was no significant difference in the strength of enemy release between the effects of monophagous versus polyphagous herbivores, terrestrial and aquatic plants, insect orders or feeding guilds and latitude of experiment. However, there were significant differences in the effects of insect herbivores between above and below ground feeders, plant growth forms, and plant organ affected.

The fundamental goal of a rare plant translocation is to create self-sustaining populations with the evolutionary resilience to persist in the long term. Yet, most plant translocation syntheses focus on a few factors influencing short-term benchmarks of success (e.g., survival and reproduction). Short-term benchmarks can be misleading when trying to infer future growth and viability because the factors that promote establishment may differ from those required for long-term persistence. We assembled a large (n = 275) and broadly representative data set of well-documented and monitored (7.9 years on average) at-risk plant translocations to identify the most important site attributes, management techniques, and species' traits for six life-cycle benchmarks and population metrics of translocation success. We used the random forest algorithm to quantify the relative importance of 29 predictor variables for each metric of success. Drivers of translocation outcomes varied across time frames and success metrics. Management techniques had the greatest relative influence on the attainment of life-cycle benchmarks and short-term population trends, whereas site attributes and species' traits were more important for population persistence and long-term trends. Specifically, large founder sizes increased the potential for reproduction and recruitment into the next generation, whereas declining habitat quality and the outplanting of species with low seed production led to increased extinction risks and a reduction in potential reproductive output in the long-term, respectively. We also detected novel interactions between some of the most important drivers, such as an increased probability of next-generation recruitment in species with greater seed production rates, but only when coupled with large founder sizes. Because most significant barriers to plant translocation success can be overcome by improving techniques or resolving site-level issues through early intervention and management, we suggest that by combining long-term monitoring with adaptive management, translocation programs can enhance the prospects of achieving long-term success.

Purpose As the UN Sustainable Development Goals (SDGs) have been widely adopted since 2015, higher education institutions (HEIs) are experimenting with ways they can be measured, reported and incorporated into all realms of the university. In this process, the challenges of SDG integration into HEIs have become more evident, from lack of resources and sustainability literacy to having multiple disconnected programs that feature the SDGs. Design/methodology/approach A mixed methods approach using archival materials, literature reviews, interviews and participant observation has been adopted for a case study at a university in the process of adopting the SDGs in multiple areas. Findings The University of South Florida began with efforts to incorporate SDGs at the undergraduate level, such as the Global Citizens Project that brands both events and courses with SDGs. Institutional changes coupled with the launch of the Times Higher Education University Impact Rankings provided more opportunities to have broader conversations about SDGs in all areas of campus.

Seed dispersal by animals is an important plant-animal mutualism, but saurochory, the dispersal of seeds by reptiles, is an understudied phenomenon despite its prevalence in many taxa. The effects of seed ingestion by the gopher tortoise (Gopherus polyphemus) were investigated in eight central Florida plant species by comparing germination of ingested seeds to seeds that did not pass through tortoises. Seeds from both treatments were also planted with and without tortoise scat. Both the percentage of seeds germinating and the time to germination were recorded. Ingested seeds from two fleshy-fruited plant species germinated in greater proportions and in less time than control seeds. The presence of scat also increased germination proportion following gut passage and decreased time to germination in both these species. Germination proportions in five dry-fruited native species were either not affected, or lowered, and time to germination was either not affected, or slower. Similarly, the effects of scat had either no effect on germination percentage in these species or caused a decrease, and either had no effect on time to germination or caused an increase. One non-native dry-fruited species was also tested, and although germination percentage following gut passage was unaffected, time to germination decreased. Similarly, while the addition of scat increased germination percentage, there was no effect on time to germination. In summary only seeds from fleshy-fruited plant species were consistently positively impacted by passage through gopher tortoise guts and by gopher tortoise scat.

Mammalian herbivores often alter plant species richness and diversity, but such impacts have not been much investigated in reptiles. This study examined the effects of gopher tortoise (Gopherus polyphemus) herbivory on species richness, Gini-Simpson diversity, and dominance, plant abundance, and biomass. Tortoise herbivory was eliminated in five areas through the use of exclosure plots for a period of two years and was compared to five similar areas where tortoises were allowed to feed. Cafeteria feeding trials were also used to quantify dietary preference. Tortoise exclosure plots had lowered species richness, and significantly lowered diversity, but significantly higher dominance than in controls. Heliotropium polyphyllum, the most highly preferred local species by tortoises, was the most dominant plant in exclosure and control plots and became even more dominant in exclosure plots. The abundance and biomass of the next two most common plant species, Fimbristylis cymosa and Polypremum procumbens, which are not preferred by tortoises, were reduced in the exclosures, probably due to increased competition with Heliotropium. Several rare plant species were eliminated in the exclosure plots. We conclude that tortoise herbivory may directly influence plant community assembly by reducing preferred plant species and promoting the growth of non-preferred species.

Gall-inducing insects seem to have a diversity pattern distinct from the usual latitudinal decrease in species, with more species occurring in xeric environments instead. Many questions regarding galler diversity over geographical scales remain unanswered: for example, little is known about beta diversity, and the role super host plants play in local/regional richness. Our aim was to compare galling insect and host plant diversity in different biogeographical regions, but under similar environmental conditions. We sampled short stature coastal woodlands on sandy soils of the Atlantic coast in both USA (Florida) and Brazil (Rio Grande do Sul, RS), between 25° and 30° latitude. Little-used 200-m long trails were searched during 90 min for galls; there were four trails in USA and five in Brazil. Gall functional traits (galled plant organ, gall shape and colour) proportions were not different between Florida and RS. Local galling and host plant species richness also did not differ, and neither did regional galling diversity. The beta diversity pattern, however, was distinct: sites in Florida have more similar galling faunas than sites in RS. Common diversity patterns indicate common environmental biotic (plant diversity, vegetation structure) and abiotic (climate, soil) factors might be contributing to these similar responses. As Brazilian sites are in the Atlantic forest hotspot, a high galling insect beta diversity might be caused by a higher heterogeneity at larger scales-sample-based rarefaction curves were ascending for Brazil, but not for USA. Myrtaceans were super hosts in Brazil, but not in Florida, where oaks take up this role.

With such great species diversity, it is unsurprising that the mangrove ecosystem harbors many complex ecological interactions. Even within each mangrove we observe a world teeming with biodiversity- we enter the realm of endophytes. The diverse and innumerable fungal and bacterial species create a unique chemical environment, affecting not only the trees themselves, but also the other residents of the mangrove community. Isolated endophytes produce many bioactive metabolites, with pathogens one would associate with the tropical mangrove environment. We have begun to observe the ecological interactions these endophytes and their secondary metabolites have on the invertebrate herbivores that predate the three species of mangroves found in costal Florida, white (Laguncularia racemosa), red (Rhizophora mangle), and black (Avicenna germinans). Identification and quantification of leaf tissue damage alongside a metabolomic study of the fungal metabolites, allows us to outline the ecological significance for the endophytes.

Interspecific competition between phytophagous insects using the same host plant occurs frequently and can strongly affect population densities of competing species. Competition between gallmakers and stemborers could be especially intense because both types of herbivore are unable to avoid competition by relocation during their immature stages. For apical meristem gallmakers the main result of competition is likely to be the interruption of resources to the gall by the stemborers' devouring of stem contents. The proximate effect of such competition could be to reduce gall size, thereby increasing the number of chambers per gall unit volume, and reducing the size and potential reproductive output of the gallformer. In addition, smaller galls may be more susceptible to attack from size-limited parasitoids, resulting in a second indirect effect of competition. Using a community of galling and stemboring insects on the saltmarsh shrub Iva frutescens L. (Asteraceae), we measured for indirect effects of competition. We examined the primary indirect effect of competition on gall midge crowding and the secondary effects on parasitism rates and parasitoid guild composition. Results indicated that galls co-occurring with stemborers were smaller, crowding of gall inhabitants was 22% greater, and the composition of the parasitoid guild was altered relative to galls on unbored stems. The overall parasitism rate was not different between galls on bored vs. unbored stems. These results show that competition resulting from the presence of stemborers has the potential to affect the gall midge Asphondylia borrichiae Rossi & Strong (Diptera: Cecidomyiidae) and secondarily to affect its guild of hymenopteran parasitoids.

Rising atmospheric CO 2 concentrations may alter the nitrogen (N) content of ecosystems by changing N inputs and N losses, but responses vary in field experiments, possibly because multiple mechanisms are at play. We measured N fixation and N losses in a subtropical oak woodland exposed to 11 years of elevated atmospheric CO 2 concentrations. We also explored the role of herbivory, carbon limitation, and competition for light or nutrients in shaping the response of N fixation to elevated CO 2 . Elevated CO 2 did not significantly alter gaseous N losses, but lower recovery and deeper distribution in the soil of a long-term 15 N tracer indicated that elevated CO 2 increased leaching losses. Elevated CO 2 had no effect on nonsymbiotic N fixation, and had a transient effect on symbiotic N fixation by the dominant legume. Elevated CO 2 tended to reduce soil and plant concentrations of iron, molybdenum, phosphorus, and vanadium, nutrients essential for N fixation. Competition for nutrients and herbivory likely contributed to the declining response of N fixation to elevated CO 2 . These results indicate that positive responses of N fixation to elevated CO 2 may be transient and that chronic exposure to elevated CO 2 can increase N leaching. Models that assume increased fixation or reduced N losses with elevated CO 2 may overestimate future N accumulation in the biosphere.

One of the most commonly cited hypotheses explaining invasion success is the enemy release hypothesis (ERH), which maintains that populations are regulated by coevolved natural enemies where they are native but are relieved of this pressure in the new range. However, the role of resident enemies in plant invasion remains unresolved. We conducted a field experiment to test predictions of the ERH empirically using a system of native, introduced invasive, and introduced non-invasive Eugenia congeners in south Florida. Such experiments are rarely undertaken but are particularly informative in tests of the ERH, as they simultaneously identify factors allowing invasive species to replace natives and traits determining why most introduced species are unsuccessful invaders. We excluded insect herbivores from seedlings of Eugenia congeners where the native and invasive Eugenia co-occur, and compared how herbivore exclusion affected foliar damage, growth, and survival. We found no evidence to support the ERH in this system, instead finding that the invasive E. uniflora sustained significantly more damage than the native and introduced species. Interestingly, E. uniflora performed better than, or as well as, its congeners in terms of growth and survival, in spite of higher damage incidence. Further, although herbivore exclusion positively influenced Eugenia seedling survival, there were few differences among species and no patterns in regard to invasion status or origin. We conclude that the ability of E. uniflora to outperform its native and introduced non-invasive congeners, and not release from insect herbivores, contributes to its success as an invader in Florida.

1. Associational resistance (AR) occurs when a plant species experiences less herbivory when growing in the presence of other plant species than when growing in monoculture. Densities of the gall midge Asphondylia borrichiae Rossi & Strong on the coastal plant Iva frutescens L. are depressed in the presence of a second coastal plant species, Borrichia frutescens (L.). Previous studies suggested that hymenopteran parasitoids from Borrichia galls spill over onto Iva galls and reduce gall densities.2. This study employs large-scale addition or near-complete removal of Borrichia from a series of spoil islands near the west central Florida coast. Densities of galls on Iva decreased where Borrichia was added, increased where Borrichia was removed and remained unchanged on islands where Borrichia abundance was not manipulated.3. Relative to unmanipulated islands, the total parasitism rate on Iva galls and parasitism rate by Torymus umbilicatus, the parasitoid hypothesised to be primarily responsible for AR in the system, declined on islands where Borrichia was removed and increased on islands where Borrichia was added, supporting the idea of parasitoid-mediated AR.

One particularly compelling explanation for the success of invasive species is the ability to outperform other species in characteristics affecting fitness. Past studies have compared native or introduced non-invasive species to their invasive counterparts, while a system incorporating both native and introduced non-invasive congeners provides an opportunity for multiple controls. We used such a system of Eugenia congeners in Florida to compare seedling performance. In order to determine if invasive Eugenia uniflora seedlings outperform those of its congeners, we sowed seeds in the field and a common garden and quantified seedling emergence, growth, and survival, as well as foliar damage by insect herbivores. We obtained similar results in the field and garden experiments. Although there were no differences in seedling emergence for E. uniflora seedlings when compared to some of its introduced congeners in certain years, emergence of E. uniflora seedlings was consistently high across years. However, emergence, growth, and survival rates of native species were consistently low. In addition, E. uniflora outperformed its introduced and native congeners in growth and survival traits in most comparisons, even when sustaining higher levels of herbivore damage by an introduced weevil, Myllocerus undatus Marshall. Our results support our predictions, indicating that invasive E. uniflora may possess a competitive advantage because its seedlings perform better than or equivalently to its congeners in all of the attributes quantified. Our study further suggests that measurements of such traits may be useful in determining the likelihood of invasion by newly introduced woody plant species.

Disturbance affects most terrestrial ecosystems and has the potential to shape their responses to chronic environmental change. Scrub-oak vegetation regenerating from fire disturbance in subtropical Florida was exposed to experimentally elevated carbon dioxide (CO₂) concentration (+350 μl l(-1)) using open-top chambers for 11 yr, punctuated by hurricane disturbance in year 8. Here, we report the effects of elevated CO₂ on aboveground and belowground net primary productivity (NPP) and nitrogen (N) cycling during this experiment. The stimulation of NPP and N uptake by elevated CO₂ peaked within 2 yr after disturbance by fire and hurricane, when soil nutrient availability was high. The stimulation subsequently declined and disappeared, coincident with low soil nutrient availability and with a CO₂ -induced reduction in the N concentration of oak stems. These findings show that strong growth responses to elevated CO₂ can be transient, are consistent with a progressively limited response to elevated CO₂ interrupted by disturbance, and illustrate the importance of biogeochemical responses to extreme events in modulating ecosystem responses to global environmental change.