Comparing the Invasibility of Experimental “Reefs” with Field Observations of Natural Reefs and Artificial Structures

Natural systems are increasingly being modified by the addition of artificial habitats which may facilitate invasion. Where invaders are able to disperse from artificial habitats, their impact may spread to surrounding natural communities and therefore it is important to investigate potential factors that reduce or enhance invasibility. We surveyed the distribution of non-indigenous and native invertebrates and algae between artificial habitats and natural reefs in a marine subtidal system. We also deployed sandstone plates as experimental ‘reefs’ and manipulated the orientation, starting assemblage and degree of shading. Invertebrates (non-indigenous and native) appeared to be responding to similar environmental factors (e.g. orientation) and occupied most space on artificial structures and to a lesser extent reef walls. Non-indigenous invertebrates are less successful than native invertebrates on horizontal reefs despite functional similarities. Manipulative experiments revealed that even when non-indigenous invertebrates invade vertical “reefs”, they are unlikely to gain a foothold and never exceed covers of native invertebrates (regardless of space availability). Community ecology suggests that invertebrates will dominate reef walls and algae horizontal reefs due to functional differences, however our surveys revealed that native algae dominate both vertical and horizontal reefs in shallow estuarine systems. Few non-indigenous algae were sampled in the study, however where invasive algal species are present in a system, they may present a threat to reef communities. Our findings suggest that non-indigenous species are less successful at occupying space on reef compared to artificial structures, and manipulations of biotic and abiotic conditions (primarily orientation and to a lesser extent biotic resistance) on experimental “reefs” explained a large portion of this variation, however they could not fully explain the magnitude of differences

Red-shouldered Hawk feeds on carrion

Volume: 36Start Page: 152End Page: 15

Mute Swan (\u3ci\u3eCygnus olor\u3c/i\u3e)

Of the 7 species of swans that have been documented in Florida, only the non-breeding Tundra Swan (Cygnus columbianus) is native. The other 6 species, including the Mute Swan, have been imported into Florida and then released at various lakes across the state for aesthetic purposes. Mute Swans are native from Great Britain, Scandinavia, and Russia south through central Europe to the Balkans, Turkey, Kazakhstan, Siberia, and northern China

Black-bellied Whistling-Duck (\u3ci\u3eDendrocygna autumnalis)

The range expansion of Black-bellied Whistling-Ducks into and throughout Florida in recent decades has been astonishing

Density and reproductive success of Florida grasshopper sparrows following fire

Information on the response of the endangered Florida grasshopper sparrow (Ammodramus savannarum floridanus Mearns) to range management, especially prescribed fire, is needed to determine conservation strategies. Intensive management of grasslands for cattle grazing and conversion of grassland to other agricultural use is considered the greatest threat to the sparrow. Territory spot-mapping and estimates of reproductive success were examined in relation to time post-burn in managed cattle pastures at Avon Park Air Force Range, Highlands County, Florida from 1997-1999. We tested the hypothesis that sparrow density and reproductive success did not depend on time following fire. Contrary to previous work, there was no evidence that Florida grasshopper sparrow territory density depended on years post-burn (P = 0.842). The probability of reproductive success was significantly higher 0.5 year post-burn than at 1.5 years post-burn (P 0.27 for each pairwise comparison between years). No simple trend or highly significant polynomial relationship between reproductive success and territory density was indicated (P > 0.41). Compared to other subspecies, Florida grasshopper sparrows exhibited relatively low density (0.22 territories/ha or less) and reproductive success (20%). Our results suggest increased reproductive success at a population level 0.5 year following fire, and did not suggest an association between territory density and individual reproductive success. Additional information is needed on the effects of seasonality of fire on Florida grasshopper sparrows.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202

Biology of Invasive Monk Parakeets in South Florida

Monk Parakeets (Myiopsitta monachus) have been in Florida for \u3e40 yrs, having been imported by the thousands for the pet trade. This conspicuous, charismatic species is now widely established, but relatively little is known about its population biology outside South America. We examined 845 parakeets from 385 nests from nest removals and collections by utility company personnel in 2003/2004 and 2006/2007 to document body size and aspects of reproductive biology and primary molt. Body measurements confirm Monk Parakeets in south Florida belong to the monachus subspecies. Adult males averaged 1.5 to 3.5% larger than females, but the body mass of females exceeded that of males during March–May, the period of egg development. The breeding season in south Florida commences in late winter/early spring with fledglings first appearing in the second week of June. Nest contents (eggs plus nestlings) averaged 5.6 for multiple-entry nests compared to 4.9 for single-entry nests. Over 94% of the adults we examined were replacing primary feathers during June–August. The extent and timing of breeding and molt in south Florida are virtually identical to those in South America, although offset by ~6 months. Monk Parakeets in south Florida retain a fixed annual cycle characteristic of the ancestral population, but their flexible behavior enables them to adapt and thrive in new environments