scholarly journals At the invasion front, male cane toads ( Rhinella marina ) have smaller testes

2019 ◽  
Vol 15 (7) ◽  
pp. 20190339 ◽  
Author(s):  
Christopher R. Friesen ◽  
Richard Shine
Keyword(s):  
Testis Size ◽  
Adult Males ◽  
Trade Off ◽  
Rhinella Marina ◽  
Invasion Front ◽  
Southeastern Australia ◽  
Invasion Stage ◽  
Invasion Fronts ◽  
Northwestern Australia ◽  
Range Core

As a colonizing species expands its range, individuals at the invasion front experience different evolutionary pressures than do those at the range-core. For example, low densities at the edge of the range mean that males should rarely experience intense sperm competition from rivals; and investment into reproduction may trade-off with adaptations for more rapid dispersal. Both of these processes are predicted to favour a reduction in testis size at the invasion front. To explore effects of invasion stage in Australian cane toads ( Rhinella marina ), we collected and dissected 214 adult males from three regions: one in the species' range-core (northeastern Australia), and two from invasion fronts (one in northwestern Australia and one in southeastern Australia). Despite the brief duration of separation between toads in these areas (approx. 85 years), testis masses averaged greater than 30% higher (as a proportion of body mass) in range-core males than in conspecifics sampled from either vanguard of the invasion. Previous work has documented low reproductive frequencies in female cane toads at the invasion front also, consistent with the hypothesis that evolutionary and ecological pressures unleashed by an invasion can favour relatively low resource allocation to reproduction in both sexes.

scholarly journals The accelerating anuran: evolution of locomotor performance in cane toads ( Rhinella marina , Bufonidae) at an invasion front

2020 ◽  
Vol 287 (1938) ◽  
pp. 20201964 ◽  
Author(s):  
Cameron M. Hudson ◽  
Marta Vidal-García ◽  
Trevor G. Murray ◽  
Richard Shine
Keyword(s):  
Morphological Traits ◽  
High Speed ◽  
Morphological Changes ◽  
Locomotor Performance ◽  
Rhinella Marina ◽  
Invasion Front ◽  
In Captivity ◽  
Tropical Australia ◽  
Range Core ◽  
Locomotor Ability

As is common in biological invasions, the rate at which cane toads ( Rhinella marina ) have spread across tropical Australia has accelerated through time. Individuals at the invasion front travel further than range-core conspecifics and exhibit distinctive morphologies that may facilitate rapid dispersal. However, the links between these morphological changes and locomotor performance have not been clearly documented. We used raceway trials and high-speed videography to document locomotor traits (e.g. hop distances, heights, velocities, and angles of take-off and landing) of toads from range-core and invasion-front populations. Locomotor performance varied geographically, and this variation in performance was linked to morphological features that have evolved during the toads' Australian invasion. Geographical variation in morphology and locomotor ability was evident not only in wild-caught animals, but also in individuals that had been raised under standardized conditions in captivity. Our data thus support the hypothesis that the cane toad's invasion across Australia has generated rapid evolutionary shifts in dispersal-relevant performance traits, and that these differences in performance are linked to concurrent shifts in morphological traits.

scholarly journals An evolutionary trade-off between parasite virulence and dispersal at experimental invasion fronts

2020 ◽  
Author(s):  
Louise N rgaard ◽  
Giacomo Zilio ◽  
Camille Saade ◽  
Claiire Gougat Barbera ◽  
Matthew Hall ◽  
...  
Keyword(s):  
Trade Off ◽  
Invasion Fronts

scholarly journals Stress and immunity at the invasion front: a comparison across cane toad (Rhinella marina) populations

2015 ◽  
Vol 116 (4) ◽  
pp. 748-760 ◽  
Author(s):  
Gregory P. Brown ◽  
Crystal Kelehear ◽  
Catherine M. Shilton ◽  
Benjamin L. Phillips ◽  
Rick Shine
Keyword(s):  
Cane Toad ◽  
Rhinella Marina ◽  
Invasion Front

Discovery of the sponge-associated caridean genus Paralebbeus in New Zealand and southeastern Australia: P. pegasus sp. nov. (Crustacea: Decapoda: Thoridae)

Zootaxa ◽  
2019 ◽  
Vol 4652 (2) ◽  
pp. 375-383
Author(s):  
SHANE T. AHYONG
Keyword(s):  
New Zealand ◽  
First Record ◽  
Northwestern Pacific ◽  
Distribution Map ◽  
Decapod Crustaceans ◽  
The Past ◽  
Southeastern Australia ◽  
Northwestern Australia ◽  
Southwestern Indian Ocean ◽  
Hexactinellid Sponges

Deepwater sampling in New Zealand and southern Australian waters over the past two decades has significantly improved knowledge of all invertebrate groups, including decapod crustaceans. Thorid shrimps of the genus, Paralebbeus Bruce & Chace, 1986 are associated with deepwater hexactinellid sponges, with four species known to date from scattered localities in the southwestern Indian Ocean, northwestern Australia, Southeast Asia and the northwestern Pacific including Japan. Paralebbeus pegasus sp. nov. is described from New Zealand and southeastern Australia, representing the first record of the genus from the temperate southwestern Pacific. The new species of Paralebbeus is unique in the genus for having meral spines on pereopods 3–5. A key to the species of Paralebbeus and global distribution map are provided. 

scholarly journals Spinal arthritis in invasive cane toads is linked to rate of dispersal as well as to latitude

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Gregory P. Brown ◽  
Lin Schwarzkopf ◽  
Ross A. Alford ◽  
Deborah Bower ◽  
Richard Shine
Keyword(s):  
Spatial Sampling ◽  
Climatic Effects ◽  
Rhinella Marina ◽  
Invasion Front ◽  
Tropical Conditions ◽  
High Incidence ◽  
Tropical Australia ◽  
Tropical Climates ◽  
Initial Research ◽  
Living Bacteria

Abstract Initial research on the spread of cane toads (Rhinella marina) through tropical Australia reported a high incidence of spinal arthritis (spondylosis) in toads at the invasion front (where toads disperse rapidly), but not in areas colonized earlier (where toads are more sedentary). The idea that spondylosis was a cost of rapid dispersal was challenged by wider spatial sampling which linked rates of spondylosis to hot (tropical) climates rather than to dispersal rates. Here, the authors of these competing interpretations collaborate to reinterpret the data. Our reanalysis supports both previous hypotheses; rates of spondylosis are higher in populations established by fast-dispersing toads, and are higher in tropical than in temperate environments; they are also higher in larger toads. The functional reason for climatic effects is unclear, but might involve effects on the soil-living bacteria involved in the induction of spondylosis; and/or may reflect higher movement (as opposed to dispersal) or more pronounced dry-season aggregation rates of toads in tropical conditions.

Interacting effects of latitude, mass, age, and sex on winter survival of Surf Scoters (Melanitta perspicillata): implications for differential migration

2016 ◽  
Vol 94 (3) ◽  
pp. 233-241 ◽  
Author(s):  
Brian D. Uher-Koch ◽  
Daniel Esler ◽  
Samuel A. Iverson ◽  
David H. Ward ◽  
W. Sean Boyd ◽  
...  
Keyword(s):  
Winter Survival ◽  
Late Winter ◽  
Adult Males ◽  
Differential Migration ◽  
Differential Survival ◽  
Melanitta Perspicillata ◽  
Adult Females ◽  
Study Sites ◽  
Range Core ◽  
Age And Sex

We quantified variation in winter survival of Surf Scoters (Melanitta perspicillata (L., 1758)) across nearly 30° of latitude on the Pacific coast of North America to evaluate potential effects on winter distributions, including observed differential distributions of age and sex classes. We monitored fates of 297 radio-marked Surf Scoters at three study sites: (1) near the northern periphery of their wintering range in southeast Alaska, USA, (2) the range core in British Columbia, Canada, and (3) the southern periphery in Baja California, Mexico. We detected 34 mortalities and determined that survival averaged lower at the range peripheries than in the range core, was lower during mid-winter than during late winter at all sites, and was positively correlated with body mass within locations. Although neither age nor sex class had direct effects, mass effects led to differential survival patterns among classes. When simultaneously incorporating these interacting influences, adult males of mean mass for their location had highest survival at the northern range periphery in Alaska, whereas adult females and juveniles had higher survival at the range core and the southern periphery. Our observations help to explain patterns of differential migration and distribution reported for this species and highlight seasonal periods (mid-winter) and locations (range peripheries) of elevated levels of mortality for demographically important age–sex classes (adult females).

scholarly journals The loneliness of the long-distance toad: invasion history and social attraction in cane toads ( Rhinella marina )

2017 ◽  
Vol 13 (11) ◽  
pp. 20170445 ◽  
Author(s):  
Jodie Gruber ◽  
Martin J. Whiting ◽  
Gregory Brown ◽  
Richard Shine
Keyword(s):  
Biological Invasion ◽  
Information Transfer ◽  
Leading Edge ◽  
High Density ◽  
Invasion History ◽  
Population Densities ◽  
Long Distance ◽  
Social Attraction ◽  
Rhinella Marina ◽  
Invasion Front

Individuals at the leading edge of a biological invasion constantly encounter novel environments. These pioneers may benefit from increased social attraction, because low population densities reduce competition and risks of pathogen transfer, and increase benefits of information transfer. In standardized trials, cane toads ( Rhinella marina ) from invasion-front populations approached conspecifics more often, and spent more time close to them, than did conspecifics from high-density, long-colonized populations.

Reduced investment in immune function in invasion-front populations of the cane toad (Rhinella marina) in Australia

2011 ◽  
Vol 14 (5) ◽  
pp. 999-1008 ◽  
Author(s):  
David Llewellyn ◽  
Michael B. Thompson ◽  
Gregory P. Brown ◽  
Benjamin L. Phillips ◽  
Richard Shine
Keyword(s):  
Immune Function ◽  
Cane Toad ◽  
Rhinella Marina ◽  
Invasion Front

BEHAVIOURAL STRATEGIES, TESTIS SIZE, AND REPRODUCTIVE SUCCESS IN TWO CAVIOMORPH RODENTS WITH DIFFERENT MATING SYSTEMS

Behaviour ◽  
1999 ◽  
Vol 136 (9) ◽  
pp. 1203-1217 ◽  
Author(s):  
Jorg Epplen ◽  
Esther Schwarz-Weig ◽  
Anja Keil ◽  
Norbert Sachser
Keyword(s):  
Body Weight ◽  
Reproductive Success ◽  
Mating System ◽  
Mating Systems ◽  
Field Studies ◽  
Testis Size ◽  
Adult Males ◽  
Natural Habitats ◽  
Single Male ◽  
Cavia Aperea

AbstractWe summarize our studies on the social and mating systems of Cavia aperea and Galea musteloides , two closely related South-American rodents. In Cavia an extremely high incompatibility exists among adult males. As a consequence, only a single male can be kept together with several females even in richly structured enclosures of 20 m2. From this, a polygynous mating system emerges. In contrast, under similar housing conditions male Galea are much more tolerant and large groups can be established consisting of several adult males and several adult females. The mating system of Galea is promiscuous because of the female's soliciting behaviour when receptive that makes it impossible for a single male to monopolize her. The diverging mating systems correspond well with functional variations in testis size and sexual dimorphism: the polygynous Cavia show low testis masses (weight of both testes = 0.58% of body weight) and body weights are 11% higher in males than in nonpregnant females. The promiscuous Galea have extremely high relative testis masses (1.86% of body weight) and non-pregnant females are 15% heavier than males. In the latter species promiscuous mating results in a high percentage of multiple paternities (> 80% in groups of 4 males and 6-7 females) as revealed by multi-locus DNA fingerprinting. Nevertheless dominant males achieve a significantly higher reproductive success than subordinates. The high frequency of overt aggression directed from dominant to subordinate males, therefore, may be a mechanism to lower the fertilizing capacity of the lower ranking males. Concerning the females' reproductive success we demonstrated in a mating experiment that Galea which were paired with four males and became pregnant, weaned significantly more offspring than females which were paired with a single male. Thus, for the first time a reproductive benefit from promiscuous mating is shown for a female mammal. Field studies in the natural habitats of Cavia aperea and Galea musteloides are now performed to elucidate whether the differences in social and mating systems can be related to differences in ecological conditions.

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