The impact of parasites during range expansion of an invasive gecko

Spatially limited pathogen pollution in an invasive tick and host system

Expansion of global commerce has facilitated pathogen pollution via the transportation and translocation of invasive species and their associated parasites and pathogens. In Florida, imported cane toads (Rhinella horribilis) were accidentally and intentionally released on multiple occasions. Early populations were found to be infested with the invasive tick, Amblyomma rotundatum, yet it is unknown if these ticks dispersed with their hosts as cane toads spread throughout much of the state. The objectives of our investigation were to (1) determine if there are fewer tick infestations on toads at the periphery than at the core of their distribution as predicted by founder effect events, and (2) identify if ticks were infected with exotic pathogens. We captured toads from 10 populations across Florida. We collected ticks, vent tissue, and tick attachment site tissue from each toad, then tested samples for bacteria in the genus, Rickettsia. We found that 3/10 populations had toads that were infested with A. rotundatum, and infested individuals were in the earliest introduced populations at the core of their distribution. Pathogen testing confirmed Rickettisa bellii in ticks, but not in toad tissues. Haplotype networks could not clearly distinguish if R. bellii in Florida was more closely related to North or South American strains, but host-tick associations suggest that the pathogen was exotic to Florida. Our investigation demonstrated that an invasive species facilitated the introduction of parasites and pathogens into Florida, yet the invasive tick species encountered limitations to dispersal on this host species.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10530-024-03291-9.

Revision of zigzag geckos (Diplodactylidae: Amalosia) in eastern Australia, with description of five new species

Geckos of the genus Amalosia Wells & Wellington, 1984 occur across eastern and northern Australia. Only five species are described but additional diversity has been recognised for some time. Here we assess species diversity in eastern Australia, using morphological and genetic (ND4 mtDNA) data. We describe five new species, all morphologically distinct and highly genetically distinct (>25% divergence). Amalosia hinesi sp. nov. is found in woodlands on the western side of the Great Dividing Range in south-east Queensland and north-east New South Wales. Amalosia saxicola sp. nov. is a large species found on rocks in the MackayTownsville areas of mid-east Queensland, including on many offshore islands. Amalosia nebula sp. nov. is restricted to rocky areas in upland sclerophyll forest of the Wet Tropics region of north-east Queensland. Amalosia capensis sp. nov. is a small species found in the northern half of Cape York Peninsula. Amalosia queenslandia sp. nov. is a small species that is widespread through woodlands over much of eastern and central Queensland. These species are diagnosed from other Amalosia species in eastern Australia, including A. cf. rhombifer which occurs in north-western Queensland. Amalosia cf. rhombifer is part of the clades comprising the remainder of the A. rhombifer complex across the Northern Territory and Western Australia, which will be dealt with separately. Herein, we also we also synonymise the monotypic genus Nebulifera with Amalosia. This revision brings the number of Amalosia species to ten.

Travelling with a parasite: the evolution of resistance and dispersal syndromes during experimental range expansion

Rapid evolutionary change during range expansions can lead to diverging range core and front populations, with the emergence of dispersal syndromes (coupled responses in dispersal and life-history traits). Besides intraspecific effects, range expansions may be impacted by interspecific interactions such as parasitism. Yet, despite the potentially large impact of parasites imposing additional selective pressures on the host, their role on range expansions remains largely unexplored. Using microcosm populations of the ciliate Paramecium caudatum and its bacterial parasite Holospora undulata, we studied experimental range expansions under parasite presence or absence. We found that the interaction of range expansion and parasite treatments affected the evolution of host dispersal syndromes. Namely, front populations showed different associations of population growth parameters and swimming behaviours than core populations, indicating divergent evolution. Parasitism reshaped trait associations, with hosts evolved in the presence of the parasite exhibiting overall increased resistance and reduced dispersal. Nonetheless, when comparing infected range core and front populations, we found a positive association, suggesting joint evolution of resistance and dispersal at the front. We conclude that host-parasite interactions during range expansions can change evolutionary trajectories; this in turn may feedback on the ecological dynamics of the range expansion and parasite epidemics.

Calling behaviour in the invasive Asian house gecko (Hemidactylus frenatus) and implications for early detection

Abstract ContextAcoustic communication is common in some animal groups, with an underlying function typically associated with mating or territoriality. Resolving the function of calls is valuable both in terms of understanding the fundamental biology of the species and, potentially, for applied reasons such as detection. Early detection is a key step in exclusion and eradication of invasive species, and calling behaviour can be used in this regard. The Asian house gecko (Hemidactylus frenatus) is one of a minority of lizards that uses acoustic communication. However, despite how conspicuous the call is, its function remains poorly resolved. It is also one of the world’s most invasive species, with exclusion via early detection being the key form of control. AimsThe aim was to resolve calling patterns and underlying function of the loud, multiple-chirp call (‘chik, chik, chik…’) in H. frenatus, in the context of using the results for developing effective methods for detection of new and establishing populations. MethodsThe calls of wild H. frenatus were recorded to assess peaks in calling activity. Also, laboratory experiments were performed to determine which individuals call, what causes them to call and the degree of call variation among individuals. Key resultsAssessment of calling behaviour in the wild revealed greater calling activity in warmer months, and five- to 10-fold peaks in calling activity at sunset and 30min before sunrise. Laboratory experiments revealed that calls were uttered exclusively by males and primarily by adults (although juveniles can call). Males called more when they were paired with females as opposed to other males. Calls differed among geckos, including the expected negative correlation between dominant frequency and body size. ConclusionsThe results suggest that the multiple-chirp call functions as a territory or sexual broadcast by males, perhaps containing information such as body size. ImplicationsDetection success can be maximised by performing acoustic surveys (by human or machine) during the calling peaks at 30min before sunrise and at sunset, particularly during warm nights. However, these surveys will only be effective for detecting adult males. The results also suggest that good quality recordings could potentially be used to identify individual geckos.

First Report of Co-invasion by the Reptile Nematode Ozolaimus megatyphlon (Nematoda: Pharyngodonidae) with Invasive Green Iguanas (Iguana iguana) in the Asia-Pacific

PURPOSE

Co-invasion of naïve ecosystems by non-native parasites is a serious threat to global biodiversity, though such events are difficult to detect early in the invasion process. Green iguanas (Iguana iguana) are an emerging invasive species and have colonised several countries in the Asia-Pacific. A survey was undertaken to determine whether parasites of the green iguana had co-invaded naïve ecosystems with their introduced host.

METHODS

Over a 10-month period, wild green iguanas were trapped and euthanised in Singapore. All animals were necropsied and sampled for parasites. Parasites were then identified morphologically and subsequently characterised molecularly at the cytochrome c oxidase I (COI) locus.

RESULTS

The reptile nematode Ozolaimus megatyphlon was found in 38% of the sampled green iguanas, with burdens of 100 + worms in all infected animals. This represents the first recorded co-invasion of this species with wild green iguanas in the Asia-Pacific. Based on the molecular characterisation of the cytochrome c oxidase I (COI) locus, the first DNA barcode is provided for O. megatyphlon.

CONCLUSION

For the first time, the reptile nematode Ozolaimus megatyphlon is shown to be invasive and to have colonised the Asia-Pacific region with its introduced host, the green iguana. The DNA barcode provided here will facilitate future monitoring programmes as O. megatyphlon invades new habitats and countries.

How epidemiological patterns shift across populations in an exotic lizard

Several factors influence the dynamics and structure of parasite communities. Our goal was to investigate how the community composition, prevalence and abundance of parasites change across seven populations of the exotic lizard Hemidactylus mabouia in Northeast Brazil, and to describe ontogenetic and sex variations. We found differences in the composition of component communities and patterns of infection according to the host body size across the lizard populations. We did not find any variation between the sexes regarding epidemiological patterns, which can probably be explained by the similar diet and habitat use of male and female H. mabouia. An unusually high abundance and prevalence of trematodes infecting this host lizard was apparent when we compared other native lizard hosts, and we suggest that local environmental conditions might be advantageous to the development and life cycle of these parasites due to the abundance of all the intermediate and definitive hosts.