Tropicalization is a term used to describe the transformation of temperate ecosystems by poleward-moving tropical organisms in response to warming temperatures. In North America, decreases in the frequency and intensity of extreme winter cold events are expected to allow the poleward range expansion of many cold-sensitive tropical organisms, sometimes at the expense of temperate organisms. Although ecologists have long noted the critical ecological role of winter cold temperature extremes in tropicaltemperate transition zones, the ecological effects of extreme cold events have been understudied, and the influence of warming winter temperatures has too often been left out of climate change vulnerability assessments. Here, we examine the influence of extreme cold events on the northward range limits of a diverse group of tropical organisms, including terrestrial plants, coastal wetland plants, coastal fishes, sea turtles, terrestrial reptiles, amphibians, manatees, and insects. For these organisms, extreme This article has been contributed to by US Government employees and their work is in the public domain in the USA.

This paper represents a DNA barcode data release for 3,400 specimens representing 521 species of fishes from 6 areas across the Caribbean and western central Atlantic regions (FAO Region 31). Merged with our prior published data, the combined efforts result in 3,964 specimens representing 572 species of marine fishes and constitute one of the most comprehensive DNA barcoding “coverages” for a region reported to date. The barcode data are providing new insights into Caribbean shorefish diversity, allowing for more and more accurate DNA-based identifications of larvae, juveniles, and unknown specimens. Examples are given correcting previous work that was erroneous due to database incompleteness.

Genetic diversity, population genetic structure and isolation by distance (IBD) were assessed in a viviparous coastal shark (the lemon shark Negaprion brevirostris) across 8 western Atlantic samples spaced between ~150 and 7000 km apart. Juveniles (N = 325) were sequenced at 2 mitochondrial loci (1729 bp) and typed at 9 nuclear encoded microsatellite loci. Analysis of mitochondrial sequences revealed higher diversity at low-latitude island samples compared to highlatitude continental samples, consistent with an equatorial center-of-origin for this species. There were 5 distinct groups across our sampling areas (Brazil, Louisiana, Cape Canaveral, Gullivan Bay and the Florida Keys/Bahamas/Virgin Islands; pairwise Φ ST = 0.07−0.87) and all but one pair of the 8 samples also exhibited significantly different haplotype frequencies (pairwise F ST = 0.10−0.51). Bayesian analysis indicated that the Brazil and Louisiana samples were generally isolated from the others, but most of the rest were diverged although still connected or recently connected by migration. In contrast, structure was only detected between the most distant sample (Brazil) and all of the others using the microsatellite markers (pairwise F ST = 0.03−0.06). There was a significant pattern of IBD for all markers and measures of genetic differentiation (r 2 = 0.65−0.81, p < 0.05− 0.01), but not after removing the Brazil sample. There was evidence that glacial and post-glacial historical processes and sex-specific differences in philopatry affected IBD. Because of the relatively fine-scale population structure of this and other large coastal shark species more attention should be paid to local processes in the conservation and fisheries management of these species.

Resolving the geographic extent and timing of coastal shark migrations, as well as their environmental cues, is essential for refining shark management strategies in anticipation of increasing anthropogenic stressors to coastal ecosystems. We employed a regional-scale passive acoustic telemetry array encompassing 300 km of the east Florida coast to assess what factors influence site fidelity of juvenile lemon sharks (Negaprion brevirostris) to an exposed coastal nursery at Cape Canaveral, and to document the timing and rate of their seasonal migrations. Movements of 54 juvenile lemon sharks were monitored for three years with individuals tracked for up to 751 days. While most sharks demonstrated site fidelity to the Cape Canaveral region December through February under typical winter water temperatures, historically extreme declines in ocean temperature were accompanied by rapid and often temporary, southward displacements of up to 190 km along the Florida east coast. From late February through April each year, most sharks initiated a northward migration at speeds of up to 64 km day−1 with several individuals then detected in compatible estuarine telemetry arrays in Georgia and South Carolina up to 472 km from release locations. Nineteen sharks returned for a second or even third consecutive winter, thus demonstrating strong seasonal philopatry to the Cape Canaveral region. The long distance movements and habitat associations of immature lemon sharks along the US southeast coast contrast sharply with the natal site fidelity observed in this species at other sites in the western Atlantic Ocean. These findings validate the existing multi-state management strategies now in place. Results also affirm the value of collaborative passive arrays for resolving seasonal movements and habitat preferences of migratory coastal shark species not easily studied with other tagging techniques.

The FACT Network (originally the Florida Atlantic Coast Telemetry working group), established in 2007, is a grassroots collaboration that is dedicated to improving the conservation and management of aquatic animals by facilitating data sharing amongst researchers using acoustic telemetry technology, providing a community for scientists, and building stakeholder partnerships. Founded along the eastern Florida coastline, FACT quickly grew in both membership and geographical range to include 93 partner groups along a large portion of the southern U.S. Atlantic seaboard and western Caribbean. This rapid expansion was facilitated by adapting FACT's policies and procedures to meet the growing needs of its members, including implementing an online data sharing system capable of exchanging information with other compatible systems designed by the Ocean Tracking Network (OTN). Less than 13 months from its inception, the FACT database housed 129.5 million detections and metadata for 5,979 tags from 101 projects (85 FACT projects and 16 OTN-based projects). Twice-yearly meetings allow FACT members to interact, building relationships between individuals, which in turn promotes collaboration and data sharing. The success of FACT is attributable to a combination of biogeographical factors; partnerships with the Animal Tracking Network, OTN, and Southeast Coastal Ocean Observing Regional Association; and active membership. In a survey of FACT members, data management services and belonging to a community ranked highest as reasons for joining the network. Future success of the FACT Network will depend on how effectively it can adapt to changing needs and conditions in the scientific landscape. In this paper, we describe the origins, philosophy, and management approach of the FACT Network, with the hope that this information can provide insights into the benefits (and limitations) of future acoustic tracking networks in other regions.