Red imported fire ant impacts on the endangered Florida grasshopper sparrow

Red imported fire ants (Solenopsis invicta) invaded peninsular Florida more than 30 years ago. Highlands and Polk counties, Florida, were probably first invaded in the late 1960s. Since then, fire ants have continued both to spread and to increase in abundance. Experimental evidence has shown that red imported fire ants may have a detrimental impact on native species, both invertebrate and vertebrate, and that these impacts may be both direct and indirect. This segment of research was designed to determine if fire ants have a negative impact on Florida grasshopper sparrow (Ammodramus savannarumfloridanus) populations at Avon Park Air Force Bombing Range, Florida. The sampling reported herein was conducted during June and October, 1997, and all analyses are restricted to data collected during those periods. As assessed by baits, fire ants were dominant on about half the sites, and absent from others. In particular, OQ Range sites tended to have fewer fire ants present, while Delta Trail sites were more heavily infested, although there were exceptions. June fire ant abundance was strongly negatively correlated with both native ant abundance (r = -0.743, P = 0.006) and native ant species richness (r = -0.730, P = 0.007). October fire ant abundance was strongly negatively correlated with both native ant abundance (r = -0.690, P = 0.013) and native ant species richness (r = -0.736, P = 0.006). The patterns of fire ant abundance as assessed by pitfalls were very similar to those determined from bait sampling. June fire ant abundance was negatively correlated (p < 0.05) with native ant richness, but other June comparisons were not statistically significant (P > 0.05). October fire ant abundance was negatively correlated (P < 0.05) with native ant richness and abundance, but other comparisons were not statistically significant (P > 0.05). There was no significant correlation between overall insect biomass as assessed by light traps and fire ant abundance as assessed by baits or pitfalls. Total biomass varied considerably among the two sample periods because of changes in overall insect abundance during different seasons. There was a negative spatial correspondence between fire ants and native invertebrates. Over most of the intensive study areas, there was a negative spatial relationship between fire ants and the abundance of native invertebrates. Over about 50% of the intensive study areas, there was a negative spatial relationship between fire ants and the abundance of Florida grasshopper sparrows, although the relationship was not as strong as that between fire ants and native invertebrates. Fire ant and native invertebrates were negatively correlated at grasshopper sparrow count locations (r =0.347, P = 0.03). A multiple regression model was fit to the data, using fire ants and native invertebrates as independent variables, and grasshopper sparrow 100-m population estimates (n = 39) as the dependent variable. The influence of fire ants on grasshopper sparrows was negative while the influence of native invertebrates was positive. However, the overall model, while suggestive, was not significant (r = 0.304, P = 0.17). Fire ant abundance was a better (negative) predictor of sparrow populations (P = 0.13) than was invertebrate abundance (P = 0.59). The overall model and influence of fire ants on sparrow populations was suggestive of a negative influence warranting analyses of data for 1998 and 1999. (Document has 93 pages

The Likely Cause of Extinction of the Tree Snail \u3ci\u3eOrthalicus Reses Reses\u3c/i\u3e (Say)

The Stock Island tree snail, Orthalicus reses reses, went extinct in its native range in the Florida Keys in 1992. Fortunately, O. r. reses has been introduced elsewhere and further reintroductions are currently planned. Before these reintroductions are implemented, it is important to try and determine which factors were most likely to have caused the decline and extinction. While habitat destruction was probably the ultimate reason why there were so few tree snails, it is likely that an interaction of habitat fragmentation and the invasion of an exotic predator caused the final decline that lead to the extinction in 1992. We examined the last 93 O. r. reses shells to infer cause of death. In addition, using surrogate Florida tree snails, Liguus fasciatus, we conducted experiments on two previously unstudied causes of mortality: predation by red imported fire ants, Solenopsis invicta, and mortality from falls caused by wind. We found that the majority of the last O. r. reses shells were intact, indicating that mammalian and bird predation were not the greatest causes of mortality. Mortality caused by wind knocking tree snails onto the rocky hammock substrate appeared to be a potential source of mortality, but few of the tree snails exhibited signs of breakage. Mortality from fire ants appears to be one of the most likely causes of the recent decline and extinction of MO. r. reses. Experiments indicated that in a semi-natural enclosure, fire ants were capable of killing all ages of L.fasciatus, even during aestivation. Fire ants are currently found throughout the last known habitat of O. r. reses and were first discovered in this area at the time of the decline

The spatial distribution of diversity between disparate taxa: Spatial correspondence between mammals and ants across South Florida, USA

Gap Analysis takes a proactive landscape-level approach to conserving native species by identifying nodes of high biological diversity. It uses vertebrate species richness as an index of overall biological diversity. However, it remains unknownwhether or not the spatial distribution of vertebrate diversity correspondswith the diversity of other taxa. We tested whether landscape-level diversity patterns corresponded between a vertebrate and an invertebrate taxon, mammals and ants, across the southern half of the Florida peninsula, USA. Composite digital maps with a 30-m spatial resolution were produced for each taxon. Spatial correspondence between the taxa was determined by normalizing and then subtracting the composite maps. There were large areas of spatial correspondence – indicating that richness between mammals and ants was similar over much of southern Florida. However, spatial correspondence occurred where the richness of both taxa was low or moderate, and areas with the highest species richness (highest 20%) for each taxon, the explicit focus of Gap Analyses, corresponded over only 8752 ha. Gap Analysis provides a much needed assessment of landscape-level diversity patterns and proactive reserve design, but it must be explicit that the results are applicable for vertebrate diversity, which does not necessarily correspond with diversity patterns of other taxa. The two taxa investigated differ by orders of magnitude in the scale that they perceive their environment, and it is likely that diversity hotspots vary as the scale of investigation – and the taxa mapped – vary

Red imported fire ant impacts on the endangered Florida grasshopper sparrow

Red imported fire ants (Solenopsis invicta) invaded peninsular Florida morethan 30 years ago. Highlands and Polk counties, Florida, were probably first invaded inthe late 1960s. Since then, fire ants have continued both to spread and to increase inabundance. Experimental evidence has shown that red imported fire ants may have adetrimental impact on native species, both invertebrate and vertebrate, and that theseimpacts may be both direct and indirect. This segment of research was designed todetermine if fire ants have a negative impact on Florida grasshopper sparrow(Ammodramus savannarumfloridanus) populations at Avon Park Air Force BombingRange, Florida. The sampling reported herein was conducted during June and October,1997, and all analyses are restricted to data collected during those periods. As assessedby baits, fire ants were dominant on about half the sites, and absent from others. Inparticular, OQ Range sites tended to have fewer fire ants present, while Delta Trail siteswere more heavily infested, although there were exceptions. June fire ant abundance wasstrongly negatively correlated with both native ant abundance (r = -0.743, P = 0.006) andnative ant species richness (r = -0.730, P = 0.007). October fire ant abundance wasstrongly negatively correlated with both native ant abundance (r = -0.690, P = 0.013) andnative ant species richness (r = -0.736, P = 0.006). The patterns of fire ant abundance asassessed by pitfalls were very similar to those determined from bait sampling. June fireant abundance was negatively correlated (p 0.05). October fire antabundance was negatively correlated (P 0.05). There was nosignificant correlation between overall insect biomass as assessed by light traps and fireant abundance as assessed by baits or pitfalls. Total biomass varied considerably amongthe two sample periods because of changes in overall insect abundance during differentseasons. There was a negative spatial correspondence between fire ants and nativeinvertebrates. Over most of the intensive study areas, there was a negative spatialrelationship between fire ants and the abundance of native invertebrates. Over about50% of the intensive study areas, there was a negative spatial relationship between fireants and the abundance of Florida grasshopper sparrows, although the relationship wasnot as strong as that between fire ants and native invertebrates. Fire ant and nativeinvertebrates were negatively correlated at grasshopper sparrow count locations (r =0.347,P = 0.03). A multiple regression model was fit to the data, using fire ants andnative invertebrates as independent variables, and grasshopper sparrow 100-m populationestimates (n = 39) as the dependent variable. The influence of fire ants on grasshoppersparrows was negative while the influence of native invertebrates was positive.However, the overall model, while suggestive, was not significant (r = 0.304, P = 0.17).Fire ant abundance was a better (negative) predictor of sparrow populations (P = 0.13)than was invertebrate abundance (P = 0.59). The overall model and influence of fire antson sparrow populations was suggestive of a negative influence warranting analyses ofdata for 1998 and 1999. (Document has 93 pages)Research Work Order no. 175Final report

Structure-activity relationships for the antileishmanial and antitrypanosomal activities of 1'-substituted 9-anilinoacridines.

Members of the class of 9-anilinoacridine topoisomerase II inhibitors bearing lipophilic electron-donating 1'-anilino substituents are active against both the promastigote and amastigote forms of the parasite Leishmania major. A series of analogues of the known 1'-NHhexyl lead compound were prepared and evaluated against L. major in macrophage culture to further develop structure-activity relationships (SAR). Toxicity toward mammalian cells was measured in a human leukemia cell line, and the ratio of the two IC50 values (IC50(J)/IC50(L)) was used as a measure of the in vitro therapeutic index (IVTI). A 3,6-diNMe2 substitution pattern on the acridine greatly increased toxicity to L. major without altering mammalian toxicity, increasing IVTIs over that of the lead compound. The 2-OMe, 6-Cl acridine substitution pattern used in the antimalarial drug mepacrine also resulted in potent antileishmanial activity and high IVTIs. Earlier suggestions of the utility of 2'-OR groups in lowering mammalian cytotoxicity were not borne out in this wider study. A series of very lipophilic 1'-NRR (symmetric dialkylamino)-substituted analogues showed relatively high antileishmanial potency, but no clear trend was apparent across the series, and none were superior to the 1'-NH(CH2)5Me subclass. Subsets of the most active 1'-N(R)(CH2)5Me- and 1'-N(alkyl)2-substituted compounds against L. major were also evaluated against Leishmania donovani, Trypanosoma cruzi, and Trypanosoma brucei, but no consistent SAR could be discerned in these physiologically diverse test systems. The present study has confirmed earlier conclusions that lipophilic electron-donating groups at the 1'-position of 9-anilinoacridines provide high activity against L. major, but the SAR patterns observed do not carry over to the other parasites studied

Zwilch, a New Component of the ZW10/ROD Complex Required for Kinetochore Functions

The Zeste-White 10 (ZW10) and Rough Deal (ROD) proteins are part of a complex necessary for accurate chromosome segregation. This complex recruits cytoplasmic dynein to the kinetochore and participates in the spindle checkpoint. We used immunoaffinity chromatography and mass spectroscopy to identify the Drosophila proteins in this complex. We found that the complex contains an additional protein we name Zwilch. Zwilch localizes to kinetochores and kinetochore microtubules in a manner identical to ZW10 and ROD. We have also isolated a zwilch mutant, which exhibits the same mitotic phenotypes associated with zw10 and rod mutations: lagging chromosomes at anaphase and precocious sister chromatid separation upon activation of the spindle checkpoint. Zwilch's role within the context of this complex is evolutionarily conserved. The human Zwilch protein (hZwilch) coimmunoprecipitates with hZW10 and hROD from HeLa cell extracts and localizes to the kinetochores at prometaphase. Finally, we discuss immunoaffinity chromatography results that suggest the existence of a weak interaction between the ZW10/ROD/Zwilch complex and the kinesin-like kinetochore component CENP-meta