Temperature,size, reproductive allocation,and life‐history evolution in a gregarious caterpillar

The present study aimed to investigate the relationship between growth rate, final mass, and larval development, as well as how this relationship influences reproductive trade‐offs, in the context of a gregarious life‐style and the need to keep an optimal group size. We use as a model two sympatric populations of the pine processionary moth Thaumetopoea pityocampa, which occur in different seasons and thus experience different climatic conditions. Thaumetopoea pityocampa is a strictly gregarious caterpillar throughout the larval period, which occurs during winter in countries all over the Mediterranean Basin. However, in 1997, a population in which larval development occurs during the summer was discovered in Portugal, namely the summer population (SP), as opposed to the normal winter population (WP), which coexists in the same forest feeding on the same host during the winter. Both populations were monitored over 3 years, with an assessment of the length of the larval period and its relationship with different climatic variables, final mass and adult size, egg size and number, colony size, and mortality at different life stages. The SP larval period was reduced as a result of development in the warmer part of the year, although it reached the same final mass and adult size as the WP. Despite an equal size at maturity, a trade‐off between egg size and number was found between the two populations: SP produced less but bigger eggs than WP. This contrasts with the findings obtained in other Lepidoptera species, where development in colder environments leads to larger eggs at the expense of fecundity, but corroborates the trend found at a macro‐geographical scale for T. pityocampa, with females from northern latitudes and a colder environment producing more (and smaller) eggs. The results demonstrate the importance of the number of eggs in cold environments as a result of an advantage of large colonies when gregarious caterpillars develop in such environments, and these findings are discussed in accordance with the major theories regarding size in animals. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 340–349.     

Geographical variation in reproductive traits and trade‐offs between size and number of eggs in the king ratsnake,Elaphe carinata

We collected gravid king ratsnakes (Elaphe carinata) from three geographically separated populations in Chenzhou (CZ), Lishui (LS) and Dinghai (DH) of China to study the geographical variation in female reproductive traits and trade‐offs between the size and number of eggs. Not all reproductive traits varied among the three populations. Of the traits examined, five (egg‐laying date, post‐oviposition body mass, clutch size, egg mass and egg width) differed among the three populations. The egg‐laying date, ranging from late June to early August, varied among populations in a geographically continuous trend, with females at the most northern latitude (DH) laying eggs latest, and females at the most southern latitude (CZ) laying eggs earliest. Such a trend was less evident or even absent in the other traits that differed among the three populations. CZ and DH females, although separated by a distance of approximately 1100 km as the crow flies, were similar to each other in most traits examined. LS females were distinguished from CZ and DH females by the fact that they laid a greater number of eggs, but these were smaller. The egg size–number trade‐off was evident in each of the three populations and, at a given level of relative fecundity, egg mass was significantly greater in the DH population than in the LS population. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 701–709.     

Geographic variation in reproductive traits and trade-offs between size and number of eggs of the Chinese cobra (Naja atra)

We collected gravid Chinese cobras (Naja atra) from one island (Dinghai) and three mainland (Yiwu, Lishui and Quanzhou) populations in south‐eastern China to study geographical variation in female reproductive traits and the trade‐off between the size and number of eggs. We then conducted an common experiment on cobras from two of the four populations to further identify factors contributing to the observed trade‐offs. The mean size (snout–vent length) of the smallest five reproductive females increased with increasing latitude. Oviposition occurred between late June and early August, with females from the warmer localities laying eggs earlier than those from the colder localities. Maternal size was a major determinant of the reproductive investment in all populations, with larger females producing not only more but also larger eggs. Clutch size was more variable than egg size within and among populations. The observed geographical variation in clutch size, egg size, clutch mass and post‐oviposition body condition was not a simple consequence of variation in maternal size among populations, because interpopulation differences in these traits were still evident when the influence of maternal size was removed. The upper limit to reproductive investment was more likely to be set by the space availability in the island population, but by the resource availability in the three mainland populations. Trade‐offs between size and number of eggs were detected in all populations, with females that had larger clutches for their size having smaller eggs. Egg size at any given level of relative fecundity differed among populations, primarily because of interpopulation differences in the resource availability rather than the space availability. Except for the timing date of oviposition and the mean size of the smallest five reproductive females, all other examined traits did not vary in a geographically continuous trend. The common garden experiment, which standardized environmental factors, synchronized the timing date of oviposition, but it did not modify the conclusion drawn from the gravid females collected from the field. The observed geographical variation in the female reproductive traits could be attributed to the consequence of the effects of either proximate or ultimate factors. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85 , 27–40.     

Higher investment in flight morphology does not trade off with fecundity estimates in a poleward range‐expanding damselfly

1. Evolutionary increases in dispersal‐related traits are frequently documented during range expansions. Investment in flight‐related traits is energetically costly and a trade‐off with fecundity may be expected during range expansion. 2. However, in contrast to wing‐dimorphic species, this trade‐off is not general in wing‐monomorphic species. In the absence of a dispersal‐‐fecundity trade‐off, an increased investment in clutch size at the expansion front is expected possibly at a cost of reduced offspring size. 3. The study evaluated investment in female flight morphology and fecundity‐related traits (clutch size, hatchling size) and potential trade‐offs among these traits in replicated populations of the poleward range‐expanding damselfly Coenagrion scitulum. 4. Females at the expansion front had a higher relative thorax length, indicating an increased investment in flight; this can be explained by spatial sorting of dispersal ability or in situ natural selection at the expansion front. Edge females produced larger hatchlings, however, this pattern was totally driven by the population‐specific thermal larval regimes and could not be attributed to the range expansion per se. By contrast, clutch sizes did not differ between core and edge populations. There was no signal of a dispersal–fecundity trade‐off either for a trade‐off between clutch size and hatchling size. 5. These results indicate that evolution of a higher dispersal ability at the expansion front of C. scitulum does not trade off with investment in fecundity, hence a dispersal–fecundity trade‐off is unlikely to slow down range expansion of this species.     

Trade-offs between life-history traits in a coldwater fish in the Mediterranean Sea: the case of blue whiting Micromesistius poutassou

A combination of traditional and emerging methodologies was used to assess the trade-offs between several life-history traits (linked to reproduction and condition) and parasitism in a commercially-exploited cold-water species, blue whiting Micromesistius poutassou, in the Mediterranean Sea. The use of histological and gravimetric methods revealed conflicting evidence as to the fecundity type (indeterminate or determinate) of this species. Moreover, there seem to be condition-mediated compensations between egg quality and egg quantity. The effects of parasitism on reproduction and condition are species-specific and occur mainly at high intensities of infection; they include a lower batch fecundity (affecting reproductive potential), a higher hepatosomatic index and a higher spleen-somatic index. Considering the fact that larger fish spawn more eggs and that the minimum landing size is lower than the size at maturity, these results may have implications for the future management of M. poutassou stocks in the Mediterranean Sea. Local environmental conditions may account for geographical differences regarding infection in M. poutassou. Altogether, the results support the idea that the complex trade-offs between parasitism, reproduction and condition need to be considered in order to understand the status of cold-water species such as M. poutassou.     

Climate and mammalian life histories

Mammals display considerable geographical variation in life history traits. To understand how climatic factors might influence this variation, we analysed the relationship between life history traits – adult body size, litter size, number of litters per year, gestation length, neonate body mass, weaning age and age at sexual maturity – and several environmental variables quantifying the seasonality and predictability of temperature and precipitation across the distribution range of five terrestrial mammal groups. Environmental factors correlated strongly with each other; therefore, we used principal components analysis to obtain orthogonal climatic predictors that could be used in multivariate models. We found that in bats, primates and even‐toed ungulates adult body size tends to be larger in species inhabiting cold, dry, seasonal environments, whereas in carnivores and rodents a smaller body size is characteristic of warm, dry environments, suggesting that low food availability might limit adult size. Species inhabiting cold, dry, seasonal habitats have fewer, larger litters and shorter gestation periods; however, annual fecundity in these species is not higher, implying that the large litter size of mammals living at high latitudes is probably a consequence of time constraints imposed by strong seasonality. On the other hand, the number of litters per year and annual fecundity were greater in species inhabiting environments with higher seasonality in precipitation. Lastly, we found little evidence for specific effects of environmental variability. Our results highlight the complex effects of environmental factors in the evolution of life history traits in mammals. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 719–736.     

Spatial and environmental effects on Coho Salmon life history trait variation

Adult size, egg size, fecundity, and mass of gonads are affected by trade‐offs between reproductive investment and environmental conditions shaping the evolution of life history traits among populations for widely distributed species. Coho salmon Oncorhynchus kisutch have a large geographic distribution, and different environmental conditions are experienced by populations throughout their range. We examined the effect of environmental variables on female size, egg size, fecundity, and reproductive investment of populations of Coho Salmon from across British Columbia using an information theoretic approach. Female size increased with latitude and decreased with migration distance from the ocean to spawning locations. Egg size was lowest for intermediate intragravel temperature during incubation, decreased with migration distance, but increased in rivers below lakes. Fecundity increased with latitude, warmer temperature during the spawning period, and river size, but decreased in rivers below lakes compared with rivers with tributary sources. Relative gonad size increased with latitude and decreased with migration distance. Latitude of spawning grounds, migratory distance, and temperatures experienced by a population, but also hydrologic features—river size and headwater source—are influential in shaping patterns of reproductive investment, particularly egg size. Although, relative gonad size varied with latitude and migration distance, how gonadal mass was partitioned gives insight into the trade‐off between egg size and fecundity. The lack of an effect of latitude on egg size suggests that local optima for egg size related to intragravel temperature may drive the variation in fecundity observed among years.     

Amphibians live longer at higher altitudes but not at higher latitudes

Why and how organisms differ in life‐history strategies across their range is a long‐standing topic of interest to evolutionary ecologists. Although many studies have addressed this issue for several life‐history traits, such as body size and clutch size, very few have been made for some others traits, including longevity. In the present study, we performed a comparative study aiming to develop general patterns of geographical variation in longevity of urodele and anuran amphibians using published information on demographic age derived from skeletochronology. We conducted within‐species meta‐analyses using datasets of two (ten urodele and 12 anuran species) and multiple (two urodele and nine anuran species) spatially‐separated populations and found that maturation, mean, and maximum age all increased with altitude but not with latitude in each sex of both amphibian groups. This geographical pattern held true across 33 urodele and 86 anuran species at common body sizes, independent of phylogeny. It is likely that metabolic rate, reproductive investment, and mortality risk, which are the key factors that affect longevity as suggested by ageing theory, vary systemically along altitudinal gradients but not along latitudinal gradients. The evolutionary causes behind these puzzling patterns deserve further investigation. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 623–632.     

Geographical patterns of genetic variation in rosemary (Rosmarinus officinalis) in the Mediterranean basin

Climate changes during the Quaternary had important effects on the evolution of European plant species. The distribution of genetic variability in rosemary, a strictly Mediterranean species of reputed Plio‐Quaternary origin for which the diversification centre is hypothesized to be located in the western part of the Mediterranean basin, was investigated across the species range by using plastid microsatellites [plastid simple sequence repeat (cpSSR)] markers. Seven out of the 17 primer pairs screened were polymorphic, with up to four alleles, yielding a total of 17 size variants combined into ten haplotypes. A permutation test to investigate for geographical structure showed no significant differences between R_ST and G_ST, indicating that the species lacks geographical structure. Low correlation between genetic and geographical distances was shown by the Mantel test. Bayesian analysis identified two coancestry groups of populations. The distribution of genetic diversity supports the hypothesized origin in the western Mediterranean basin, and with the demographic expansion test indicates three different routes of migration: a northern route expanding along the northern side of the Mediterranean and two southern routes, one from west to east through North Africa and reaching Cyrenaica, and a second to the south‐west of the Iberian Peninsula, from where it came back to the south–central areas. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013 , 171 , 700–712.     

Fecundity selection does not vary along a large geographical cline of trait means in a passerine bird

Local environmental and ecological conditions are commonly expected to result in local adaptation, although there are few examples of variation in phenotypic selection across continent‐wide spatial scales. We collected standardized data on selection with respect to the highly variable plumage coloration of pied flycatcher (Ficedula hypoleuca Pall.) males from 17 populations across the species' breeding range. The observed selection on multiple male coloration traits via the annual number of fledged young was generally relatively weak. The main aim of the present study, however, was to examine whether the current directional selection estimates are associated with distance to the sympatric area with the collared flycatcher (Ficedula albicollis Temminck), a sister species with which the pied flycatcher is showing character displacement. This pattern was expected because plumage traits in male pied flycatchers are changing with the distance to these areas of sympatry. However, we did not find such a pattern in current selection on coloration. There were no associations between current directional selection on ornamentation and latitude or longitude either. Interestingly, current selection on coloration traits was not associated with the observed mean plumage traits of the populations. Thus, there do not appear to be geographical gradients in current directional fecundity selection on male plumage ornamentation. The results of the present study do not support the idea that constant patterns in directional fecundity selection would play a major role in the maintenance of coloration among populations in this species. By contrast, the tendency for relatively weak mosaic‐like variation in selection among populations could reflect just a snapshot of temporally variable, potentially environment‐dependent, selection, as suggested by other studies in this system. Such fine‐grained variable selection coupled with gene flow could maintain extensive phenotypic variation across populations. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 808–827.     

Population genetics,gene flow,and biogeographical boundaries of Carcinus aestuarii (Crustacea: Brachyura: Carcinidae) along the European Mediterranean coast

Carcinus aestuarii Nardo, 1847 is a widespread coastal crab species throughout the Mediterranean Sea with a pelagic larval phase. This species tolerates a wide range of environmental conditions and typically inhabits fragmented habitats, such as embayments, lagoons and estuaries. It is therefore a good candidate species for studying and testing different phylogeographical hypotheses in the Mediterranean Sea. By contrast to its Atlantic sister species, Carcinus maenas, studies on the population genetic structure of C. aestuarii in its native range are still scarce. In the present study, specimens from along the European Mediterranean Sea were collected and DNA‐sequenced and analyses were applied to discriminate between present day and historical factors influencing the population genetic structure of this species. The results obtained demonstrate the existence of two genetically distinct geographical groups, corresponding to the eastern and western Mediterranean, with further subdivision within the East Mediterranean Basin. A strong asymmetric gene flow was recorded toward the Eastern Basin, which may play a crucial role in shaping the present day biogeographical patterns of this species and potentially other sympatric ones with pelagic larvae. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 771–790.     

Large-scale intraspecific variation in life-history traits of European freshwater fish

Aims To test the magnitude and direction of the effects of large‐scale environmental factors (latitude and habitat type: lotic or lentic) on the intraspecific variations in multiple life‐history traits, across multiple European freshwater fish species. To test the relevance of defining species traits by quantifying the magnitude of interspecific vs. intraspecific variability in traits. Location Europe. Methods We obtained estimates of 11 fish traits from published sources for 1089 populations of 25 European freshwater fish species. Traits were: longevity, maximal length, growth rate, asymptotic length, mortality rate, age and length at maturation, fecundity, egg size, gonadosomatic index, and length of breeding season. We described population habitats by latitude and habitat type (lotic or lentic), when available. For each species we tested the combined effect of latitude and habitat type on the intraspecific variation of each trait using analysis of covariance (ancova ). We compared the intraspecific variation in traits with the variation between species using an analysis of variance (anova ) for each trait, all species pooled. Results We found a consistent effect in direction of latitude on six traits, but we showed that this effect is not always significant across species. Higher‐latitude populations often grew more slowly, matured later, had a longer life span and a higher maximal and asymptotic length, and allocated more energy to reproduction than populations at lower latitudes. By contrast, we noted only a slight effect of habitat type on the intraspecific variation in traits, except for Salmo trutta. All traits varied significantly between species. However, traits such as growth rate, mortality rate and length of breeding season varied more between populations than between species, whereas fecundity and traits associated with body length varied more between species. Main conclusions Latitude, in contrast to habitat type, is an important factor influencing several traits of geographically widely dispersed populations of multiple European freshwater fish species. Species traits that vary more between species than between populations are attractive variables for understanding and predicting the responses of stream fish communities to their environment.     

Effects of climate on pine processionary moth fecundity and on its egg parasitoids

Climate change may be affecting the fecundity of phytophagous insects as well as impacting their natural enemies. However, temperature impacts these two insect groups differently, disrupting population regulation mechanisms, and ultimately, possibly culminating in an outbreak of the host. The pine processionary moth (PPM) is one of the most harmful insects of the Mediterranean basin. Not only are PPM larvae harmful to plants, but they are also dangerous to humans because of their urticating hairs. Although some information is available on climate change effects on the PPM, little is known about its potential effects on PPM egg parasitoids, especially on their distribution range or on their role in controlling PPM populations. The aim of this article was to verify the effects of climate on PPM fecundity and on its egg parasitoids. Our results show that climate warming may affect the PPM positively, but not its egg parasitoids. Specifically, during our study mild winters directly favored the PPM, while increasing summer temperatures (over 30°C) also favored the PPM indirectly, by decreasing parasitism rates. We predict that ever‐milder winters will not only favor PPM development, but also encourage it to spread in otherwise previously inhospitable environments.     

Does host determine short‐range flight capacity of trichogrammatids?

Biological traits, such as body size, fecundity and fertility, of egg parasitoids are strongly influenced by host species, and the use of a single‐host species for consecutive generations has been showed to be detrimental for egg parasitoid biology. Besides biological traits, behaviour of egg parasitoids is also an important parameter for implying their performance in the field, but information about the effect of host on the behaviour of egg parasitoids is still scarce. Thus, this work aimed at determining the influence of host species on the short‐range flight capacity of three egg parasitoids Trichogrammatoidea annulata De Santis, Trichogramma atopovirilia Oatman and Platner and Trichogramma bruni Nagajara reared on Anagasta kuehniella (Zeller), Corcyra cephalonica (Stainton) and Sitotroga cerealella (Olivier), for first, 10 and 28 consecutive generations. Trichogrammatids emerged inside a tubular dark flight chamber, under controlled conditions, and short‐range flying response was based on the proportions of adults trapped to the sticky top of the chamber and the ones found on the bottom, which were checked for defective wings. Our data clearly demonstrate that trichogrammatid short‐range flight depends on the fasctidious host species. All three egg parasitoids had their flight capacity significantly reduced when emerged from S. cerealella. The highest flying capacity of T. annulata was registered when reared on C. cephalonica, while for T. atopovirilia was on A. kuehniella and T. bruni on both C. cephalonica and A. kuehniella. Parasitoid flight capacity is affected when reared on the same host over generations; however, it was not possible to define a pattern for any of the trichogrammatids. Our findings are of great relevance for quality control of mass‐reared egg parasitoids because measuring only behavioural traits with use of flight chambers can be more practical and less time‐consuming than assessing biological parameters.     

Landscape‐scale life‐history gradients in New Zealand freshwater fish

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The relationship between egg load and fecundity among Trichogramma parasitoids

1. The relationships between parasitoid egg load, size, and age (3–72 h) for Trichogramma minutum, T. platneri, and T. pretiosum, reared from two factitious hosts, Ephestia kuehniella and Sitotroga cerealella, were evaluated to test the hypothesis that 24‐h egg load can be used to estimate the fecundity of Trichogramma parasitoids. 2. Egg load increased in relation to female age over the first 3 days of adult life for all three Trichogramma species to a mean egg storage capacity of 46.7 eggs for T. minutum, 41.1 for T. pretiosum, and 35.7 for T. platneri. At 24 h of age, T. minutum had matured enough eggs to fill 67% of its storage capacity, in comparison with 74% for T. pretiosum and 91% for T. platneri. There was a positive relationship between egg load and parasitoid size for all ages of the three Trichogramma species reared from both hosts (with the exception of T. platneri at 3 h post emergence), accounting for 14–69% of the variance in egg load. 3. The potential fecundity, realised (3 day cumulative) fecundity, and oviposition rate (potential fecundity/longevity) of T. platneri were all related linearly to size‐dependent variation in 24‐h egg load, but only the realised fecundity of T. pretiosum, and none of the reproductive characteristics of T. minutum. It is suggested that 24‐h egg load may not be an accurate measure of egg storage capacity in parasitoids and should be used cautiously to represent fecundity. 4. The potential fecundity of seven Trichogramma species reared from E. kuehniella varied from 55 to 150, but neither potential fecundity nor oviposition rate was related significantly to egg load (represented by eggs laid during first 24 h). Selection to avoid egg depletion in the attack of gregarious hosts appears most likely to account for the variation in potential fecundity among Trichogramma species.     

Is it really you,Orthotrichum acuminatum? Ascertaining a new case of intercontinental disjunction in mosses

Intercontinental disjunct distributions are a main issue in current biogeography. Bryophytes usually have broad distribution ranges and therefore constitute an interesting subject of study in this context. During recent fieldwork in western North America and eastern Africa, we found new populations of a moss morphologically similar to Orthotrichum acuminatum. So far this species has been considered to be one of the most typical epiphytic mosses of the Mediterranean Basin. The new findings raise some puzzling questions. Do these new populations belong to cryptic species or do they belong to O. acuminatum, a species which then has a multiple‐continent disjunct range? In the latter case, how could such an intercontinental disjunction be explained? To answer these questions, an integrative study involving morphological and molecular approaches was conducted. Morphological results reveal that Californian and Ethiopian samples fall within the variability of those from the Mediterranean Basin. Similarly, phylogenetic analyses confirm the monophyly of these populations, showing that O. acuminatum is one of the few moss species with a distribution comprising the western Nearctic, the western Palaearctic and Palaeotropical eastern Africa. Pending a further genetic and phylogeographical study to support or reject the hypothesis, a process of long‐distance dispersal (LDD) is hypothesized to explain this distribution and the origin of the species is suggested to be the Mediterranean Basin, from where diaspores of the species may have migrated to California and Ethiopia. The spore release process in O. acuminatum is revisited to support the LDD hypothesis, © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2016, 180 , 30–49.     

The evolution of sexual size dimorphism in cottontail rabbits (Sylvilagus,Leporidae)

In mammals, ‘female‐biased’ sexual size dimorphism (SSD), in which females are larger than males, is uncommon. In the present study, we examined Sylvilagus, a purported case of female‐biased SSD, for evolutionary correlations among species between SSD, body‐size, and life‐history variables. We find that: (1) although most species are female‐biased, the degree and direction of SSD vary more than was previously recognized and (2) the degree of SSD decreases with increasing body size. Hence, Sylvilagus provides a new example, unusual for a female‐biased taxon, in which allometry for SSD is consistent with ‘Rensch's Rule’. As a corollary to Rensch's Rule, we observe that changes in SSD in Sylvilagus are typically associated with larger, more significant changes in males than females. Female‐biased SSD could be produced by selection for larger females, smaller males, or both. Although larger female size may be related to high fecundity and the extremely rapid fetal and neonatal growth in Sylvilagus, we find little evidence for a correlation between SSD and various fecundity‐related traits in among‐species comparisons. Smaller male size may confer greater reproductive success through greater mobility and reduced energetic requirements. We propose that a suite of traits (female dispersion, large male home ranges, reduced aggression, and a promiscuous mating system) has favoured smaller males and thus influenced the evolution of SSD in cottontails. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 141–156.     

Reproductive strategies of sub-Antarctic lithodid crabs vary with habitat depth

We present the first fecundity and egg size data for three species of lithodid crab from Antarctic waters south of the Polar Front, caught in the fisheries operating around the island of South Georgia. In all species, fecundity was observed to increase with body size, but reproductive allocation was found to differ significantly between species. The highest relative fecundity (eggs^−g body weight) and smallest egg size was found in Paralomis spinosissima, which is found in shallower waters, whereas the lowest relative fecundity values and largest eggs were recorded in the deeper living species, Neolithodes diomedeae. Evidence is presented that closely related sympatric species may employ quite different reproductive strategies that suit their depth distribution whilst indicating the overriding evolutionary adaptation of reproductive traits to temperature and food availability.     

House mouse dispersal in Iron Age Spain: a geometric morphometrics appraisal

During the Iron Age, sea trade in the Mediterranean increased, particularly with the expansion of Phoenician and Greek colonies in the Western Mediterranean. A side effect of these human movements was the involuntary dispersion of commensal species, such as the house mouse (Mus musculus domesticus). One archaeological layer dated from the 4th Century BC, coming from an Iberian village located in the Mediterranean coast of Spain, contained a large and reliable accumulation of small mammals. The presence of the house mouse was highly suspected within this layer. To assess its abundance quantitatively, we used a geometric morphometrics approach of the first lower molar contour using elliptical Fourier analysis. We also increased the power of the discrimination between the Algerian mouse (Mus spretus) and the house mouse by combining a dimension reduction approach together with different validation procedures. The relative importance of age, sex, and geographical origin onto the shape and form of the lower molar contour was also investigated. The results obtained demonstrate the presence and the dominance of the house mouse in the landscape surrounding the Iberian village in the 1st Millennium BC, only a few centuries after its arrival in the Western Mediterranean Basin. A cross‐validated linear discriminant function considering different Mediterranean populations suggest Morocco and France as the most probable geographical origins for the Algerian mouse, and Tunisia for the origin of house mice in North‐Eastern Spain. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 483–497.