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1. Experimental increases in temperature mean and variance alter reproductive behaviours in the dung beetle Phanaeus vindex

   https://doi.org/10.1098/rsbl.2022.0109  

   Kirkpatrick, William H. ; Sheldon, Kimberly S. ( July 2022 , Biology Letters)

   Temperature profoundly impacts insect development, but plasticity of reproductive behaviours may mediate the impacts of temperature change on earlier life stages. Few studies have examined the potential for adult behavioural plasticity to buffer offspring from the warmer, more variable temperatures associated with climate change. We used a field manipulation to examine whether the dung beetle Phanaeus vindex alters breeding behaviours in response to temperature changes and whether behavioural shifts protect offspring from temperature changes. Dung beetles lay eggs inside brood balls made of dung that are buried underground. Brood ball depth impacts the temperatures offspring experience with consequences for development. We placed adult females in either control or greenhouse treatments that simultaneously increased temperature mean and variance. We found that females in greenhouse treatments produced more brood balls that were smaller and buried deeper than controls, suggesting brood ball number or burial depth may come at a cost to brood ball size, which can impact offspring nutrition. Despite being buried deeper, brood balls from the greenhouse treatment experienced warmer mean temperatures but similar amplitudes of temperature fluctuation relative to controls. Our findings suggest adult behaviours may partially buffer developing offspring from temperature changes. 

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2. Contrasting plant adaptation strategies to latitude in the native and invasive range of Spartina alterniflora

   https://doi.org/10.1111/nph.16371  

   Liu, Wenwen ; Zhang, Yihui ; Chen, Xincong ; Maung‐Douglass, Keith ; Strong, Donald R. ; Pennings, Steven C. ( January 2020 , New Phytologist)

   Biological invasions offer model systems of contemporary evolution. We examined trait differences and evolution across geographic clines among continents of the intertidal grassSpartina alterniflorawithin its invasive and native ranges.

   We sampled vegetative and reproductive traits in the field at 20 sites over 20° latitude in China (invasive range) and 28 sites over 17° in the US (native range). We grew both Chinese and US plants in a glasshouse common garden for 3 yr.

   Chinese plants werec. 15% taller,c. 10% denser, and set up to four times more seed than US plants in both the field and common garden. The common garden experiments showed a striking genetic cline of seven‐fold greater seed set at higher latitudes in the introduced but not the native range. By contrast, there was a slight genetic cline in some vegetative traits in the native but not the introduced range.

   Our results are consistent with others showing that introduced plants can evolve rapidly in the new range.S. alterniflorahas evolved different trait clines in the native and introduced ranges, showing the importance of phenotypic plasticity and genetic control of change during the invasion process.

    

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3. Differential learning by native versus invasive predators to avoid distasteful cleaning mutualists

   https://doi.org/10.1111/1365-2435.13806  

   Tuttle, Lillian J. ; Lamb, Robert W. ; Stringer, Allison L. ( May 2021 , Functional Ecology)

   Cleaning symbioses on coral reefs are mutually beneficial interactions between two individuals, in which a ‘cleaner’ removes and eats parasites from the surface of a ‘client’ fish. A suite of behavioural and morphological traits of cleaners signal cooperation with co‐evolved species, thus protecting the cleaner from being eaten by otherwise predatory clients. However, it is unclear whether cooperation between cleaners and predatory clients is innate or learned, and therefore whether an introduced predator might consume, cooperate with or alter the behaviour of cleaners.

   We explored the role of learning in cleaning symbioses by comparing the interactions of native cleaner fishes with both naïve and experienced, non‐native and native fish predators. In so doing, we tested the vulnerability of the predominant cleaners on Atlantic coral reefs, cleaning gobies (Elacatinusspp.), to the recent introduction of a generalist predator, the Indo‐Pacific red lionfish (Pterois volitans).

   Naïve juveniles of both invasive (P. volitans) and native predators (Cephalopholisspp. groupers) initially attacked cleaning gobies and hyperventilated from a putative toxin on the gobies' skin during laboratory experiments. After one to five such encounters, invasive lionfish often approached the cleaner closely, then turned away without striking. Consistent with learned avoidance, invasive lionfish rarely interacted with cleaning gobies in the wild, either antagonistically or cooperatively, and did not affect gobies' abundance. Native predators showed little evidence of learning during early encounters; they repeatedly attacked the cleaner during laboratory experiments and hyperventilated less violently than did lionfish. However, consistent with learned cooperation, native predators rarely antagonised and were frequently cleaned by gobies in the wild.

   We demonstrated that rapid, learned avoidance protects a distasteful cleaning mutualist from an invasive predator. The behavioural plasticity of this invader likely contributes to its success across its invaded range. Additionally, our results suggest that the cleaner's chemical defence most likely evolved as a way to deter predation and reinforce cooperation with naïve individuals of native species.

    

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4. Elucidating mechanisms of invasion success: Effects of parasite removal on growth and survival rates of invasive and native frogs

   https://doi.org/10.1111/1365-2664.13634  

   Roznik, Elizabeth A. ; Surbaugh, Kerri L. ; Cano, Natalia ; Rohr, Jason R. ; Driscoll, ed., Don ( May 2020 , Journal of Applied Ecology)

   Identifying the mechanisms underlying biological invasions can inform the management of invasive species. The enemy release hypothesis (ERH) suggests that invasive species have a competitive advantage in their introduced range because they leave behind many of their predators and parasites from their native range, allowing them to shift resources from defences to growth, reproduction and dispersal. Many studies have demonstrated that invasive species have fewer parasites than their native counterparts, but few studies have tested whether the loss of these natural enemies appears to be a primary driver of the invasion process.

   To test the ERH, we conducted a mark–recapture study in which we used an anthelmintic drug to successfully reduce parasitic worms in invasive Cuban treefrogsOsteopilus septentrionalisand native treefrogs (Hylaspp.) at half of 12 wetlands, marking nearly 4,200 frogs. If the ERH is supported, we would expect that treating for parasitic worms would have a greater benefit to native than invasive hosts.

   Growth and survival rates of invasive and native treefrogs responded similarly to the anthelmintic treatment, suggesting that the Cuban treefrog's release from parasitic worms does not appear to significantly contribute to its invasiveness in established areas. Instead, it appears that the overall faster rates of growth and maturation, higher survival rates and larger body sizes of Cuban treefrogs that we observed may contribute to their expansion and proliferation.

   Synthesis and applications. Although Cuban treefrogs have a lower diversity of parasitic worms in their invasive than native range, this does not appear to significantly contribute to their invasion success in areas where they have been established for more than 20 years. This suggests that any manipulation of parasites in invasive or native hosts would not be an effective method of controlling Cuban treefrogs or reducing their impacts. Further research into other hypotheses is needed to explain the Cuban treefrog's success and help guide management actions to reduce their spread and negative impacts. Our study demonstrates that enemy release may not be a primary driver of invasiveness, highlighting the need for more experimental tests of the enemy release hypothesis to examine its generality.

    

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5. Biogeographic variation of distance‐dependent effects in an invasive tree species

   https://doi.org/10.1111/1365-2435.13306  

   Yang, Qiang ; Ding, Jianqing ; Siemann, Evan ; Godoy, ed., Oscar ( March 2019 , Functional Ecology)

   Plant pathogens and herbivores can maintain forest diversity by reducing survival of tree seedlings close to conspecifics. However, how biogeographic variation in these natural enemies affects such distance‐dependent processes is unknown. Because invasive plants escape ecologically important enemies when introduced to a new range, distance‐dependent mortality may differ between their native and introduced ranges.

   Here, we test whether the invasive treeTriadica sebiferaescaped distance‐dependent mortality when introduced to the United States from China, and examine the roles of natural enemies in native and introduced ranges. In both the United States and China, we performed field surveys along with field and greenhouse experiments with field‐collected soils and soil sterilization treatments.

   In field surveys and the field experiment, insect damage onT. sebiferaseedlings decreased with distance to conspecific trees in the native range (China), but damage was low at all distances in the introduced range (United States). In the greenhouse experiment testing the effects of soil pathogens,T. sebiferaseedling mortality decreased with soil distance from conspecific trees in both ranges but distance‐independent mortality was higher in native range soils.

   Our findings indicate that both insect herbivores and the soil biota contribute to distance‐dependent effects onT. sebiferain its native range. They suggest, however, that plants may more readily escape herbivore than soil biota distance‐dependent effects when introduced to a new range and so herbivores, rather than soil pathogens, contribute more strongly to biogeographic variation in distance‐dependent effects. These results highlight the importance of considering species biogeographic variation in distance‐dependent effects and teasing apart the roles that different natural enemies play when studying species coexistence, community diversity and biological invasions.

    

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