Goals, Justification and Main Findings
The goal of this paper was to “assess the influence of predatory eastern newts, Notophthalmus viridescens, on the outcome of interspecific competition among native and non-indigenous tadpoles” (Smith 342). Research shows that when some specific keystone predators are present, diversity in the prey population improves in situations that have a competitive hierarchy amid prey species.
Nevertheless, there exists insufficient knowledge about the influence that keystone predator exerts when present in the invaded prey populations. Considering the growing concern about invasive species influence and their prevalence, research on this topic was crucial.
The research found out that “in the presence of the tadpoles of one invasive group and absence of newts, the Osteopilus septentrionalis led to the domination of the tadpole assemblage by O. septentrionalis and reduced development and survival rate of the dominant native species, Bufo terrestris” (Smith 347).
Nevertheless, a single adult newt caused similar performance and endurance of native groups in non-invaded and invaded treatments when at hand, since it commonly eradicated or condensed the negative effects of O. septentrionalis tadpoles.
Study Approach and Methods
The researcher carried out experiments through outdoor aquatic mesocosms. Black containers filled with Calcium and some well water created the mesocosms. The researcher placed some pond waste in the container to form a natural substrate. He then roofed tanks to keep metamorphic anurans awaiting collection and stop common anurans from laying eggs into the substrate.
A few days later, he put some stalks of live Hydrilla and Hydrocotyle species into every container to increase spatial density. Concurrently, he put some alfalfa pills into all experimental containers. These pills functioned as a reserve base for the marine populations.
He as well added several snails into the containers. Besides, he drew a liter of water from every container and redistributed it in all the containers to make sure that there was the consistency of the aquatic populations in the mesocosms. Lastly, he put some water from an ordinary container that had many aquatic species drawn from local pond water into each mesocosm.
The research design was a randomized block trial. The researcher used two treatment aspects to test the effect that newt predation had on the aggressiveness of the non-native tadpoles. The first aspect was an invasion action that had four dimensions denoting four substitutive blends of local and non-native larval anurans.
The substitutive blueprint offered a conventional examination of the impacts of the presence of non-native tadpoles in spite of general tadpole density considering a restricted amount of mesocosms (Smith 346). The incidence or lack of a single mature male N. viridescens was the second aspect. The researcher crossed every point of the invasion aspect with two points of a second aspect (Smith 347).
The populations used in the experiment were derived from a four species indigenous tadpole collection comprising similar numbers of “Bufo terrestris, (southern toad), Hylasquirella (squirrel treefrog), Gastrophryne carolinensis (eastern narrow-mouthed toad), and Rana sphenocephala (southern leopard frog)’’ (Smith 347).
The researcher Collected eggs in every group during a rainy period in Florida. He assembled all tadpole groups in clutches from Hillsborough and Alachua Counties. He then mixed numerous clutches of every group to cut the effects of genetics on the outcomes of this research.
Besides, he assembled twenty fully developed male N. viridescens from Rodman Reservoir and measured, weighed, and rounded off every newt to the nearest cm and mg.
He allocated every newt arbitrarily to 20 of the 40 mesocosms. Two days later, he assembled a sample of ten entities from every anuran group to prove that the larvae of all six groups were past the free-swimming phase. Also, he assigned larval anurans to every one of the 40 mesocosms arbitrary as approved by the substitutive design.
Results and Interpretation
Results indicated that the invasion treatment influenced the survival of native tadpoles considerably, in the absence of newts. Fewer populations of the dominant native group, B. terrestris, endured in the incidence of O. septentrionalis and absentia of newts.
As seen in Fig. 2a, the curve representing the number of B. terrestris in the presence of O. septentrionalis and absence of newts dropped from 0.7 to 0.6, while the curve representing the number of B. terrestris in the presence of both O. septentrionalis and newts increased upwards from 0.7 to 0.8. Thus, larval B. terrestris faced high rates of endurance when newts were present irrespective of the incidence of O. septentrionalis.
In conclusion, predatory newts influence competition amid non-indigenous and native tadpoles. As seen in the study, the number of the prey species (B. terrestris) increased when newts were a presence, since newts preyed on O. septentrionalis, exceptionally, leaving room for the multiplication of B. terrestris.
This study offers evidence that keystone predators are valuable aspects when considering the preservation of diversity in invaded areas. This implies that the idea of biotic resistance is authentic. Future research should focus on whether newts hamper the establishment or multiplication of O. septentrionalis in Florida.
Works Cited
Smith, Kevin. “Keystone Predators (Eastern Newts, Notophthalmus viridescens) Reduce the Impacts of an Aquatic Invasive Species.” Oecologia 148 (2006): 342–349. Print.