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Population Ecology and Evolutionary Ecology

I aim to conduct research that leads to a more predictive ecological science. To this end, my research approach minimizes assumptions that have not explicitly been tested in my study system. It's a not a rare feature of current ecological practice to translate the evidence of organisms taxonomically unrelated or from different environments to the study system of interest. This cannot always be avoided, due to complexity that garnishes ecology. However, in my research I enjoy minimizing assumptions and have devoted with my team quite a bit of time and energy to collect data that allows us to test those assumptions.

I am interested in understanding what are the main drivers of fitness. How does the biotic and abiotic environment interact with individual attributes to determine survival and reproduction. My research, should ultimately allow us to better understand the mechanisms that translate environmental variation into fitness currencies of interest and how that translates in variation in population growth.



Research highlights 

Below I showcase some of my research on this area including summaries of published articles 

and highlighting their main conclusions. 

                                                                                                   



From physiology to space use: energy reserves and androgenization 

explain home-range size variation in a woodland rodent

Godsall B, Coulson T, Malo AF *

Journal of Animal Ecology 83: 126-135    2014


This study tested the relationships between both individual-level and predation-risk factors and the size of two home-range regions (HRR), defined as areas of different intensities of use. We have expanded on previous home-range studies by testing the effects of two previously ignored individual-level factors: androgenization and energy reserves (body fat). Location data were collected for wild individuals of Apodemus sylvaticus using the novel method of implanted PIT tags and mobile recording stations. A total of 68 home ranges were estimated using kernel density estimation. Home ranges were split into two regions (HRR): the 'core', representing the most intensively used areas, and 'periphery' regions. Body mass, body fat, sex, anogenital distance (AGD) (a proxy for androgenization) and the proportion of HRR, covered by antipredatory features (shrubs and fallen trees), were tested for their relationship with the size of core and periphery HRRs. Models were constructed for each HRR for three seasons: nonbreeding season (NBS), early and late breeding seasons (LBSs), to account for seasonal variation in behaviour associated with changes in food abundance and reproductive cycles. Body fat had a negative relationship with periphery size and an interaction with sex on core size in the early breeding season (EBS). Body mass also had a significant interaction with sex on core size in the EBS. Androgenization has a strong effect on home range size in both sexes: AGD had a positive relationship with both HRRs for males in the LBS and females in the NBS. Males had larger peripheries than females in both early and LBSs. Habitat features that reduce predation risk explain HRR size throughout the breeding period. This study emphasizes the importance of embracing natural complexity to gain insight into the drivers of space use behaviour; the consideration of individual and ecological factors, the recognition of the species-specific selective pressures that seasonal change presents for each sex and the identification of biologically meaningful home range areas will help advance the field.

                                                                                                   



Positive effects of an invasive shrub on aggregation and abundance 

of native small rodent explain home-range size variation in a 

woodland rodent


Malo AF *, Godsall B, Prebble C, Grange Z, McCandless S, Taylor A, Coulson T. 

Behavioral Ecology 24 (3): 759-767    2013 

Invasive plants can have dramatic effects on natural ecosystems. It is unclear, though, whether these will have a positive or negative effect on animal species’ behavior and population parameters within ecosystems where invasive plants occur. Here, we use a 2-year time series of mouse trapping data to test the effects of an evergreen invasive shrub, Rhododendron ponticum, on population distribution and abundance in a population of wood mice (Apodemus sylvaticus) in southern England. Given the importance of aerial predators on rodent survival and the shield that the thick cover of Rhododendron branches and leaves provides, we predicted that Rhododendron would have a positive effect on mouse aggregation and abundance. The results confirmed both predictions: proximity to Rhododendron positively influenced mouse abundance, whereas a significant interaction between protective microhabitat features (logs) and Rhododendron suggest that reductions in predation risk drive the proximity results. In addition, as mouse densities increased, competition increased. During spring, when mouse territoriality was greatest, we found primarily large adults in the Rhododendron habitat, with subadult and juvenile mice more likely to be found away from Rhododendron patches. The effects of Rhododendron-driven increases in mouse density on lower (seed predation and dispersal) and upper trophic level (weasel populations) are also discussed. Questing tick’s density and invertebrate biomass were also lower under Rhododendron. Our research shows that an invasive plant species can increase the abundance of a native mammal and that this could potentially lead to increases/decreases in other species populations within the community.


                                                                                                   


Pedigrees and the Study of the Wild Horse Population of Assateague Island National Seashore
Eggert LS, Powell DMBallou JD, Malo AFTurner A, Kumer J, Zimmerman C, Fleisher RC, Maldonado JE2010. 
Journal of Wildlife Management 74(5):963–973         

Recently, a number of papers have addressed the use of pedigrees in the study of wild populations, highlighting the value of pedigrees in conservation management. We used pedigrees to study the horses (Equus caballus) of Assateague Island National Seashore, Maryland, USA, one of a small number of free-ranging animal populations that have been the subject of long-term studies. This pop ulation grew from 28 in 1968 to 175 in 2001, causing negative impacts on the island ecosystem. To minimize these effects, an immunocontraception program was instituted, and horse numbers are slowly decreasing. However, there is concern that this program may negatively affect the genetic health of the herd. We found that although mitochondrial DNA diversity is low, nuclear diversity is comparable to that of established breeds. Using genetic data, we verified and amended maternal pedigrees that had been primarily based on behavioral data and inferred paternity using genetic data along with National Park Service records of the historic ranges of males. The resulting pedigrees enabled us to examine demography, founder contributions, rates of inbreeding and loss of diversity over recent generations, as well as the level of kinship among horses. We then evaluated the strategy of removing individuals (using nonlethal means) with the highest mean kinship values. Although the removal strategy increased the retained diversity of founders and decreased average kinship between individuals, it disproportionately impacted sizes of the youngest age classes. Our results suggest that a combined strategy of controlled breeding and immunocontraception would be more effective than removing individuals with high mean kinships in preserving the long-term health and viability of the herd.


                                                                                                   


Simulation model for contraceptive management of the Assateague Island feral horse population using individual-based data
Ballou JD, Traylor-Holzer K, Turner A, Malo AF, Powell D, Maldonado J, Eggert L. 2008. 
Journal Wildlife Research, 35 (6): 502-512

The National Park Service (NPS) manages a culturally significant population of feral horses (Equus caballus) inhabiting the Maryland portion of Assateague Island, a barrier island in the eastern United States. Rapid growth of this population over the past few decades from 28 to 166 horses negatively impacts native species and ecological processes on the island. Since 1994, contraception via porcine zona pellucida vaccine has been used to control horse numbers, although herd reduction has been slower than initially expected, leading NPS to consider other management options. An individual-based stochastic simulation model was developed using the Vortex software program to examine the effects of different management strategies on the population. Data from the managed population were used to populate the model parameters. Model projections over the next 50 years using current management practices show an average rate of population decline of 13% per year, suggesting that the population will reach the management target of 80–100 horses in 5–8 years. The effectiveness of contraception to reduce the herd and maintain it at various target sizes of 20–100 horses was also assessed. The accumulation of inbreeding at each target population size was also modelled.    

                                                                                                   

European rabbit (Photo credit Naturlink)
Factors shaping European rabbit abundance in continuous and fragmented populations of central Spain 
Virgos E, Cabezas S, Malo AFLozano J, Huertas DL. 2003. 
Acta Theriologica 48 (1): 113–122.

This study analyses differences in European rabbit Oryctolagus cuniculus (Linnaeus,1758) abundance between fragmented and continuous populations and the relative  importance of habitat structure (micro- and macrohabitat) and isolation in determining the abundance pattern in fragmented and continuous areas of central Spain. The species was mainly restricted to Mediterranean vegetation habitat. In fragmented areas, rabbit abundance was linked to scrub land cover but was not correlated to pasture/crop-land cover. The model explained very little of the observed variance. Distance to continuous populations did not improve the model. Stochastic phenomena or unmeasured factors (predation level, soil type) could be acting in this context. Rabbits were more abundant in continuous areas than in fragmented ones. In continuous areas, rabbit abundance was associated with mosaics of pastures, scrub-lands, and croplands. These habitat features are linked to shelter and feeding requirements of rabbits. The model explained an important part of the observed variance. This supports that management and conservation strategies should be based on the landscape pattern in each situation.

                                                                                                   



A change of diet from rodents to rabbits (Oryctolagus cuniculus). Is the wildcat (Felis silvestris) a specialist predator? 
AF Malo*, J Lozano, DL Huertas, E Virgós. 2004. 
Journal of Zoology  263, 401–407 

The results of a study testing the hypothesis that wildcats Felis silvestris are rodent-specialist predators is reported.The diet of wildcats was studied in different habitats from central Spain where rabbits Oryctolagus cuniculus were either present or absent in order to explore whether the wildcat is a facultative or a rodent specialist. We predicted that if the wildcat was a rodent specialist there would be no differences in rodent composition in scats between areas with or without another profitable prey such as rabbits. To test this hypothesis, 239 scats were collected in two contrasting habitat types: Mediterranean vegetation areas, where rabbits were either present or absent, and Pyrenean oak forests,where there were no rabbits.All areas and habitat types were sampled in different seasons. The frequency of occurrence and biomass of different prey items and diet diversity were compared between habitats and areas with the presence/absence of rabbits.Wildcats consumed significantly fewer rodents in areas with rabbits than in areas where rabbits were absent, and diet diversity showed important seasonal variations. Values for diet diversity were lower in areas where rabbits were present. Thus it can be stated that wildcats do not specialize in rodents, and we suggest a facultative specialization on different prey items (rabbits or rodents) according to prey availability.


                                                                                                   


Wildcat about to be fitted with a radio collar

Wildcat about to be fitted with a radio collar (Photo AF Malo)


Importance of scrub–pastureland mosaics for wildliving cats occurrence in a Mediterranean area: implications for the conservation of the wildcat (Felis silvestris)  
J Lozano, E Virgos, AF MaloDL Huertas, JG  Casanovas. 2003. 
Biodiversity and Conservation 12: 921–935.
The  European wildcat (Felis silvestris) is a threatened species in Europe. Suitable management of forests has been considered crucial for its conservation in Europe. However, this recommendation may  not be general due to the lack of studies that test these hypotheses in the Mediterranean area, where landscapes are very different from those of central-north Europe. In this study, wild-living cat habitat associations were analyzed by means of scat surveys in 78 areas distributed in the four main vegetation types of the Mediterranean area of central Spain, where feral cat populations are probably scarce and restricted. Results show higher occurrences of wild-living cats in landscapes covered by scrub–pastureland mosaics rather than forests. Several applied recommendations are given: (1) to include the scrub–pastureland mosaics as protected habitats for wildcats; (2) to encourage further studies about the importance of this habitat in other areas; (3) to avoid the extensive scrubland removal associated with management practices against fires or infrastructure development; and (4) to promote land management practices that enhance these mosaics, and to use shrub species in the reforestation programmes founded by the European Agricultural Policy.


                                                                                                   


Known range of the European wildcat 


Conservation of European Wildcat (Felis silvestris) in Mediterranean Environments: A Reassessment of Current Threats (pp. 1-32) 
Lozano, AF Malo
In Mediterranean Ecosystems: Dynamics, Management and Conservation. 


The wildcat (Felis silvestris) is considered as a “strictly protected” species under current European legislation. The European wildcat range extends from the Iberian Peninsula to the Caucasus Mountains and up to Scotland in the north. However, its continental distribution is largely fragmented at regional and local scales. According to this fragmented pattern wildcat populations remain isolated, many of them facing real extinction risks. Under this scenario, preserving all the European populations will maximize the species viability on the long term. Even so, considering that Mediterranean populations constitute the half of the species in Europe, and even probably the best preserved populations from a genetic point of view, their conservation is expected to be especially relevant.      Several factors, such as habitat destruction, direct and indirect persecution and hybridization with domestic cats, currently threaten wildcat populations in Europe. The relative importance of different threats is expected to vary among regions and populations, but there is much demographic information lacking from these populations to adequately establish conservation issue priorities. The infiltration of domestic cat genes on the wildcat’s gene pool, i.e. introgression, is being considered one of the main threats, suggesting special conservation measures such as feral cat control in the wild,  aimed at maintaining the genetic integrity of wildcat populations. While any conservation effort is welcome, the results from most genetic analyses do not seem to justify the alarm and efforts devoted to fight introgression, especially in the Mediterranean areas, where this issue can be considered minor, as shown by studies conducted in the studied populations. On the other hand, other threats such as habitat destruction and non-natural mortality are not receiving enough attention, when these might be more urgent and among the ultimate causes of genetic introgression.     Here we highlight current knowledge gaps such as the location and size of viable wildcat populations, their demographic parameters, degree of gene flow and their main selective pressures, as well as the effect of man-induced mortality and habitat alteration on population dynamics. All these gaps, among others, hamper our ability to identify and prioritise conservation problems. Thus, we also propose throughout the text study guidelines to fill these issues, which will help get a better picture of the situation and to design effective conservation strategies. 

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