Sociobiology of Caviomorph Rodents:
An Integrative Approach
Luis A. Ebensperger
& Loren D. Hayes, Eds.
2016
Wiley Blackwell
Hoboken, NJ, USA
380 pp
$97.03
Cooperative Breeding in Vertebrates:
Studies of Ecology, Evolution, and Behavior
Walter D. Koenig &
Janis L. Dickinson, Eds.
2016
Cambridge
University Press
Cambridge, U.K.
379 pp
$115.67
In his
highly regarded book, Principles of Social Evolution
(2011), Andrew Bourke treats the origin of societies as a major
evolutionary transition characterized by control of conflict and the
appearance of castes (Table 1.3). In this author's system, castes
define a society as eusocial, “with an appreciable reproductive
division of labour, irreversible or not” (Box 1.1). Eusocial
societies with totipotent individuals, are sometimes referred to as
“primitively” eusocial (Wilson 1971), and Bourke points out (loc.
cit.) that cooperatively
breeding vertebrate societies resemble (reversible) eusocial
societies “because any level of reproductive division of labor
implies a degree of altruism” (loc. cit.).
In my own work, I follow Bourke's terminology (Jones 2014), in
addition to his use of Hamilton's (1964) schema limiting animal
(including, human) behavior to four categories (selfish, cooperative,
altruistic, and spite, Table 1 this review). In Hamilton's system,
then, “social” behavior is confined to cooperative
or altruistic
interactions between (usually) conspecifics, measured according to
differential reproductive costs or benefits to Actor and Recipient.
In
Sociobiology of Caviomorph Rodents,
Ebensperger and Hayes have performed a service by summarizing a
speciose and diverse group of primarily South American rodents
(Patterson & Upham 2014) characterized by twelve families of
which ~75% include one or more social species (including, capybaras,
tuco-tucos, cavies, maras, viscachas, and chinchillas). Since at
least 1998, Ebensperger has advocated for the use of hystricognath
rodents as a model of social evolution, and the book under review
reinforces that message documented in several chapters devoted to the
wide range of caviomorph sociosexual behaviors and structures
(Chapters 1, 2, 7-11). Additional chapters review caviomorph
neurobiology, genetics, communication, and fitness effects,
presenting a comprehensive, “integrative” approach to the group,
while, in the final chapter (Chapter 13) the editors synthesize what
we know and need to know, in their opinion, about caviomorph
sociality.
Sociobiology of Caviomorph Rodents
will appeal to specialists wishing to broaden their knowledge of
social taxa as well as to students interested in identifying
stimulating and important research topics upon which to base a
dissertation or a career. Furthermore, the potential for comparative
studies is documented by similarities in certain traits between some
caviomorph species and voles. Unfortunately, readers will need to be
tolerant of the volume's limitations such as the authors' failure to
cite more than a few references after 2012, frequent repetitions,
some annoying grammatical errors, too many instances of researchers
relying upon personal opinion and qualitative statements rather than
inferences based on measurements. Also, investigators studying
caviomorph social biology seem to have a penchant for attributing
group-living in this infraorder to predation pressure, a factor that
some specialists consider a common cause of group-formation but not
group-maintenance. Likewise, most of the authors in this text use
group size as a proxy for social behavior, a problematic assumption
seemingly resulting from defining “social” as group-living
whereby larger groups would exhibit a greater number of
interindividual interactions. As Rubenstein et al. (2016) show,
however, the evolution of sociality relative to (female) group size
is taxon-specific and rule-governed. Finally, and of significant
concern, where Hamilton's general rule is discussed at all,
statements appear naïve at best and, in some cases, incorrect (e.g.,
pages 307 and 311). This text is, nonetheless, recommended as a point
of entry to a group of rodents with significant research potential.
Indeed, rodents are the largest Order of Mammals; however, our
knowledge of their social biology is limited compared to that of
primates and carnivores, Orders with a noteworthy proportion of
social species.
In
Cooperative Breeding in Vertebrates,
cooperative breeding is broadly defined as “breeding associations
with three or more individuals collectively raising young in a single
brood or litter” (Introduction). As a result, the book covers a
wide range of taxa, behaviors, and structures. Koenig and Dickinson
chose 19 species to illustrate their topic, 15 of these chapters
covering birds, 1, fish, and 3 reports on cooperatively-breeding
mammals. The final, summary chapter by the Editors is noteworthy
because of Figure 20.3 and Table 20.1. In addition to the fact that
the descriptive studies are fascinating and informative, they are
examples of the high standards which field natural history can
attain. Authors, many with international reputations, have not only
keenly observed relevant behavioral and structural details of their
systems, but, relying, primarily, on verbal, rather than,
quantitative, models, interpret their results with an appreciation
for hypothesis-testing. For the most part, researchers rely on
descriptive statistics to illustrate their subjects and associated
traits, though a few studies incorporate genetic analyses as
tentative tests of “kin selection” theory.
Because the species
described in this text range from delayed dispersal with no
cooperative care (Siberian jays), to “marginal” cooperative
breeders (western bluebirds), to simple conformations with
single-pair breeders (superb fairy wrens) and their “helpers,” to
complex societies incorporating plural breeders (superb starlings),
the book can be read in a way that reveals patterns related to the
evolution of cooperative breeding and possible causal factors (e.g.,
distribution and abundance of limiting resources, environmental
heterogeneity, group size and composition, population demography,
predation). Finally, throughout the text, promising topics for
investigation are indicated, such as, Why does “helping” by males
appear to be common (e.g., superb fairy wrens, chestnut-crowned
babblers, bell miners, banded mongooses), and are its causal factors
different than those for female “helpers”? Also, one is curious
about “kidnapping” behavior in banded mongooses and whether it
might be induced by social parasitism or, perhaps, is a precursor to
“slavemaking” as is the case in some social insects?
Apparently,
none of the research programs in either of the books under review
utilizes multivariate analyses in an attempt to assess causality or
agent-based modeling to conduct quantitative tests of hypotheses
(but, see Chapters 3 and 18); thus, for the most part, inferences
remain speculative. Furthermore, it is not clear from the discussion
of methods in most chapters whether animals were marked, whether
focal-animal observational procedures were employed (preferably with
a randomized baseline), and in what ways field experiments were
conducted. Virtually every chapter in both books under review end
their reports by calling for more research to document variability of
target phenomena, implying that it is premature to search for general
principles within and between taxa, even though some of these studies
have proceeded for decades. As the paper by Rubenstein et al. (2016)
demonstrates, however, analyses based on central tendencies can
expose straightforward rules upon which complex phenomena depend.
Weinrich et al. (2006) demonstrated that there exists a limited
number of solutions to any evolutionary question which would include
the problems inherent to Social Biology. Sociobiology of
Caviomorph Rodents and
Cooperative Breeding in Vertebrates
deserve serious inspection by students of sociality,, animal
behavior, and behavioral ecology. However, conventional Natural
History might benefit from the incorporation of more rigorous methods
and the application of quantitative procedures.
References
Bourke
AFG (2011) Principles of social evolution.
Oxford University Press, Oxford.
Ebensperger
LA (1998) Sociality in rodents: the New World fossorial
hystricognaths as study models. Revista Chilena de
Historia Natural 71: 65-77.
Hamilton
WD (1964) The genetical theory of social behavior. J Theor
Biol 7: 1-52.
Jones
CB (2014) The evolution of mammalian sociality in an
ecological perspective.
Springer, New York.
Patterson
BD, Upham NS (2014) A study in contrasts: two extensive Neotropical
radiations. Frontiers in Ecology and Evolution
2: 1-2.
Rubenstein
DR, Botero CA, Lacey EA (2016) Discrete but variable structure of
animal societies leads to the false perception of a social
continuum. R. Soc. open sci.
3: 160147. http://dx.doi.org/10.1098//rsos.160147
Weinreich
DM, Delaney NF, DePristo MA, Hartl DL (2006) Darwinian evolution can
follow only very few mutational paths to fitter proteins. Science
312: 111-114.
Wilson
EO (1971) The insect societies.
Harvard, Cambridge, MA.
*Originally published in ISBE Newsletter, 2016
Table
1.
This table
presents Hamilton's schema depicting hypothetical outcomes of
interactions
between two (usually conspecific) individuals (a
“dyad”), including, predicted reproductive tradeoffs
(often
measured as # offspring). A “selfish” state is presumed to be
original and fundamental since
selection acts on individual genotypes
and since assisting ego’s own reproduction should benefit an
individual more than benefiting another individual's reproduction (an
individual is always related to
itself by 1.00). It follows that
“cooperation” and “altruism” have evolved where a “selfish”
strategy
cannot do its best. By definition, “cooperation” and
“altruism” require Actor (“ego”) to restrain or
compromise
some measure of its “fitness budget” by donating some measure of
reproduction to a
Recipient. In the case of “spite,” both Actor
and Recipient lose reproductive benefits as a result of
one or more
interactions.
|
|
BENEFITS
OR COSTS TO
ACTOR |
BENEFITS
OR COSTS TO
RECIPIENT |
|
SELFISH
|
+ |
- |
|
COOPERATIVE |
+ |
+ |
|
ALTRUISTIC |
_ |
+ |
|
SPITEFUL
|
_ |
- |
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