Interpopulation differences in parasite load and variable selective pressures on MHC genes in<i>Ctenomys talarum</i>

Cutrera, A; Zenuto, Roxana Rita; Lacey, Eileen A.

doi:10.1644/13-mamm-a-120

Cited by 13 publications

(16 citation statements)

References 106 publications

(159 reference statements)

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“…This finding contrasts markedly with the positive correlation between ectoparasite burden and population density of a solitary subterranean rodent, the Talas tuco-tuco (Ctenomys talarum), in Argentina (Cutrera et al 2014). It suggests that density-dependent mechanisms are unlikely to explain the observed patterns although all ectoparasites collected in the current study are directly transmitted.…”

Section: Discussioncontrasting

confidence: 99%

Digging for answers: contributions of density- and frequency-dependent factors on ectoparasite burden in a social mammal

2015

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Due to the density-dependent nature of parasite transmission parasites are generally assumed to constrain the evolution of sociality. However, evidence for a correlation between group size and parasite burden is equivocal, particularly for mammals. Host contact rates may be modified by mobility of the host and parasite as well as social barriers. In the current study, we used the common mole-rat (Cryptomys hottentotus hottentotus), a social subterranean rodent, as a model system to investigate the effect of host density and frequency of contact rates on ectoparasite burdens. To address these factors we used a study species that naturally varies in population densities and intergroup contact rates across its geographic range. We found that ectoparasite prevalence, abundance and species richness decreased with increasing host density at a regional scale. At the same time, measures of parasite burden increased with intergroup contact rates. Ectoparasite burdens decreased with colony size at the group level possibly as a result of increased grooming rates. Equating group size with population density might be too simplistic an approach when assessing parasite distributions in social mammals. Our data suggest that frequencydependent mechanisms may play a much greater role at a population level than density-dependent mechanisms in determining parasite distributions in social species. We suggest that future studies should explicitly consider behavioural mechanisms that may affect parasite distribution.

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Section: Discussioncontrasting

confidence: 99%

Digging for answers: contributions of density- and frequency-dependent factors on ectoparasite burden in a social mammal

2015

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“… Leucocyte profile was evaluated as G/L ratio (granulocyte/lymphocyte) in Kurtz et al (), as N/L ratio (neutrophil/lymphocyte) in Cutrera et al (), Cutrera et al (), as H/L ratio (heterophil/lymphocyte) in Lukasch et al (). Antibody production was evaluated against sheep red blood cell antigens (SRBC) in Bonneaud et al (), Cutrera et al (), Lukasch et al () and the present study, against diphtheria and tetanus toxoid antigens in Ekblom et al (), and against human serum albumin and tetanus toxoid antigens in the present study. …”

Section: Methodsmentioning

confidence: 99%

“… Details regarding MHC diversity: in Charbonnel et al () measured as heterozygosity at two different MHC loci (0/1, Dqa1 and Drb loci), and number of amino acid differences between alleles for both loci; in Cutrera et al (), Cutrera et al () measured as MHC heterozygosity (0/1); in Rodríguez et al () measured as the number of amino acid differences between MHC alleles; in Montano‐Frías et al () measured as the number of MHC loci present; in Lukasch et al () measured as the number of different functional MHC alleles (i.e., “supertypes,” based only on sites located within the PBR and characterized by physicochemical descriptors). Details regarding specific MHC alleles: in Cutrera et al (), Cutrera et al () presence/absence of MHC allele groups (groups defined according to their amino acid similarity); in Ekblom et al () presence/absence of specific allelic lineages (lineages defined according to their nucleotide similarity); in Rodríguez et al () presence/absence of MHC allele groups (two groups were defined based on the most frequent vs. infrequent alleles); in Montano‐Frías et al () presence/absence of specific MHC loci; in Sin et al () presence/absence of specific MHC alleles and haplotypes; in Lukasch et al () presence/absence of the most frequent functional MHC alleles (i.e., “supertypes,” based only on sites located within the PBR and characterized by physicochemical descriptors). …”

Section: Methodsmentioning

confidence: 99%

“…Less information is available from wild species' populations, with contrasting outcomes in the few studies available. Thus, whereas some studies have found support for associations of MHC variation and immunocompetence (Bonneaud, Richard, Faivre, Westerdahl, & Sorci, ; Charbonnel et al, ; Cutrera, Zenuto, & Lacey, ; Kurtz et al, ; Lukasch et al, ), others have provided no clear evidence for their existence (Bonneaud, Sinsheimer, Richard, Chastel, & Sorci, ; Cutrera, Zenuto, & Lacey, ; Ekblom, Hasselquist, & Sæther, ; Montano‐Frías, Vera‐Massieu, Álvarez‐Martínez, Flores‐Morán, & Acevedo‐Whitehouse, ; Rodríguez, Broggi, Alcaide, Negro, & Figuerola, ; Sin et al, ). Such contrasting results may indicate the absence of a general biological association between MHC variation and immunocompetence, which may arise only in certain species, populations and/or ecological contexts.…”

Section: Introductionmentioning

confidence: 99%

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Lack of statistical power as a major limitation in understanding MHC‐mediated immunocompetence in wild vertebrate populations

et al. 2019

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Disentangling the sources of variation in developing an effective immune response against pathogens is of major interest to immunoecology and evolutionary biology. To date, the link between immunocompetence and genetic variation at the major histocompatibility complex (MHC) has received little attention in wild animals, despite the key role of MHC genes in activating the adaptive immune system. Although several studies point to a link between MHC and immunocompetence, negative findings have also been reported. Such disparate findings suggest that limited statistical power might be affecting studies on this topic, owing to insufficient sample sizes and/or a generally small effect of MHC on the immunocompetence of wild vertebrates. To clarify this issue, we investigated the link between MHC variation and seven immunocompetence proxies in a large sample of barn owls and estimated the effect sizes and statistical power of this and published studies on this topic. We found that MHC poorly explained variation in immunocompetence of barn owls, with small‐to‐moderate associations between MHC and immunocompetence in owls (effect size: .1 ≥ r ≤ .3) similar to other vertebrates studied to date. Such small‐to‐moderate effects were largely associated with insufficient power, which was only sufficient (>0.8) to detect moderate‐to‐large effect sizes (r ≥ .3). Thus, studies linking MHC variation with immunocompetence in wild populations are underpowered to detect MHC effects, which are likely to be of generally small magnitude. Larger sample sizes (>200) will be required to achieve sufficient power in future studies aiming to robustly test for a link between MHC variation and immunocompetence.

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“…Mate choice may be influenced by MHC diversity (high or intermediate), compatibility (high or intermediate diversity in offspring), and/or based on specific alleles or supertypes (Ejsmond, Radwan, & Wilson, 2014). Spatial or temporal differences in mate choice for MHC characteristics may also occur (fluctuating selection, Cutrera, Zenuto, & Lacey, 2014). In some systems, sexual selection may play a large role in maintaining MHC diversity.…”

mentioning

confidence: 99%

Specific MHC class I supertype associated with parasite infection and color morph in a wild lizard population

Hacking

Stuart‐Fox

Godfrey

et al. 2018

Ecology and Evolution

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The major histocompatibility complex (MHC) is a large gene family that plays a central role in the immune system of all jawed vertebrates. Nonavian reptiles are underrepresented within the MHC literature and little is understood regarding the mechanisms maintaining MHC diversity in this vertebrate group. Here, we examined the relative roles of parasite‐mediated selection and sexual selection in maintaining MHC class I diversity of a color polymorphic lizard. We discovered evidence for parasite‐mediated selection acting via rare‐allele advantage or fluctuating selection as ectoparasite load was significantly lower in the presence of a specific MHC supertype (functional clustering of alleles): supertype four. Based on comparisons between ectoparasite prevalence and load, and assessment of the impact of ectoparasite load on host fitness, we suggest that supertype four confers quantitative resistance to ticks or an intracellular tickborne parasite. We found no evidence for MHC‐associated mating in terms of pair genetic distance, number of alleles, or specific supertypes. An association was uncovered between supertype four and male throat color morph. However, it is unlikely that male throat coloration acts as a signal of MHC genotype to conspecifics because we found no evidence to suggest that male throat coloration predicts male mating status. Overall, our results suggest that parasite‐mediated selection plays a role in maintaining MHC diversity in this population via rare‐allele advantage and/or fluctuating selection. Further work is required to determine whether sexual selection also plays a role in maintaining MHC diversity in agamid lizards.

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Interpopulation differences in parasite load and variable selective pressures on MHC genes inCtenomys talarum

Cited by 13 publications

References 106 publications

Digging for answers: contributions of density- and frequency-dependent factors on ectoparasite burden in a social mammal

Digging for answers: contributions of density- and frequency-dependent factors on ectoparasite burden in a social mammal

Lack of statistical power as a major limitation in understanding MHC‐mediated immunocompetence in wild vertebrate populations

Specific MHC class I supertype associated with parasite infection and color morph in a wild lizard population

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