Utilization of food resources by small and medium‐sized mammals in the Monte Desert biome,Argentina

Theoretical models of species coexistence between desert mammals have generally been based on a combination of food and microhabitat selection by granivorous rodents. Although these models are applicable in various deserts of the world, they cannot explain resource use by mammals in Neotropical deserts. The present study examines diet composition in a mammal assemblage in the Monte desert, Argentina. The results show that two main strategies are used by these mammals: medium‐sized species (hystricognath rodents: Dolichotis patagonum, Lagostomus maximus, Microcavia australis and Galea musteloides; and an exotic lagomorph: Lepus europaeus) are herbivores, whereas small‐sized species (a marsupial: Thylamys pusillus; and sigmodontine rodents: Graomys griseoflavus, Akodon molinae, Calomys musculinus, Eligmodontia typus) are omnivorous. Small mammals also show a tendency towards granivory (C. musculinus), insectivory (A. molinae and T. pusillus) and folivory (G. griseoflavus).     

Role of small rodents in the seed dispersal process: Microcavia australis consuming Prosopis flexuosa fruits

Understanding the functional role of animal species in seed dispersal is central to determining how biotic interactions could be affected by anthropogenic drivers. In the Monte Desert, mammals play different functional roles in Prosopis flexuosa seed dispersal, acting as opportunistic frugivores (endozoochorous medium‐sized and large mammals) or seed hoarders (some small sigmodontine rodents). Our objective was assessing the functional role of Microcavia australis, a small hystricognathi rodent, in the fruit removal and seed deposition stages of P. flexuosa seed dispersal, compared to sympatric sigmodontine rodents. In situ, we quantified fruit removal by small rodents during non‐fruiting and fruiting periods, and determined the distance seeds were transported, particularly by M. australis. In laboratory experiments, we analysed how M. australis stores seeds (through scatter‐ or larder‐hoarding) and how many seeds are left in caches as living seeds, relative to previous data on sigmodontine rodents. To conduct field studies, we established sampling stations under randomly chosen P. flexuosa trees at the Ñacuñán Man and Biosphere Reserve. We analysed fruit removal by small rodents and seed dispersal distance by M. australis using camera traps focused on P. flexuosa fruits covered with wire screen, which only allowed entry of small animals. In laboratory trials, we provided animals with a known number of fruits and assessed seed conditions after removal. Small rodents removed 75.7% of fruit supplied during the non‐fruiting period and 53.2% during the fruiting period. Microcavia australis and Graomys griseoflavus were the main fruit removers. Microcavia australis transported seeds to a mean distance of 462 cm and cached seeds mainly in scatter‐hoards, similarly as Eligmodontia typus. All transported seeds were left in fruit segments or covered only by the endocarp, never as predated seeds. Microcavia australis disperses P. flexuosa seeds by carrying fruits away from a source to consume them and then by scatter‐hoarding fruits and seeds.     

Assessment of habitat quality for four small mammal species of the Monte Desert, Argentina

In the temperate desert of Argentina, the combined action of climatic and anthropogenic factors has contributed to the formation of a highly heterogeneous landscape. In the central region of the Monte desert, four small mammal species (Eligmodontia typus, Calomys musculinus, Akodon molinae and Graomys griseoflavus) coexist and show different habitat uses in response to spatial variability. Three main habitat types are present in the region: mesquite forest, the creosotebush community and sand dunes. These habitat types are present also in the surrounding grazing area.The objective of this study was to determine habitat quality for these species in a protected area (Reserve MaB Ñacuñán) and in the adjacent grazed area. For each species we estimated demographic parameters that are highly correlated to fitness in each habitat, and for both treatments (protected and grazed).We found that the protected area offered a higher quality habitat than the grazed area for all species, but principally A. molinae and G. griseoflavus. At a local scale, we found that A. molinae and C. musculinus clearly showed higher fitness in the more complex habitats as the creosotebush community and the mesquite forest. In contrast, for E. typus, open and simplest patches, such as sand dunes, were optimal for its survival and reproduction.     

Protein polymorphism inEligmodontia typus. Genetic divergence with other phyllotine cricetids

By means of gel electrophoresis of tissue extracts we have studied protein polymorphism inEligmodontia typus. The analysis was performed on specimens from five population samples collected at different sites in Patagonia (Argentina). Mean heterozygosity (\-h) and proportion of polymorphic loci (P) were determined on the basis of 19 loci. Considering all individuals as one sample, \-h gave a value of 0.16 and P was 70%. Although these values are much higher than those reported for most rodent species, they are very similar to those obtained by us for four species of the genusCalomys and forGraomys griseoflavus. There is a striking genetic identity (I_N=0.99) among populations from regions with different environmental conditions, indicating that the species possesses a common genic pool. Genetic distance with other species of the Phyllotini was estimated. D_N was lower betweenE. typus andCalomys (mean D_N=0.88) than betweenE. typus andGraomys griseoflavus (D_N=1.01). The high morphological similarity between these last two species, especially regarding those characters related to desert life adaptation, could be assigned, at least in part, to convergent evolution.     

Seed hoarding by rodents of the Monte Desert,Argentina

Food storage is an important adaptation of several animal species to the temporally variable or unpredictable food supplies that are typical of desert environments. In the present study, whether Eligmodontia typus and Graomys griseoflavus inhabiting sand dunes in the Monte desert displayed scatter‐hoarding was investigated. Both rodent species prepared surface caches by digging small holes (1–3 cm deep) in the soil. Caches were partially covered with sand and dry leaves, which meant that all of the cache sites at each station could be found. Most caches were found below shrubs, that is, in a sheltered microhabitat rather than near the food source. The mean distance between caches and seed sources was significantly higher than the mean distance from food sources to shrubs. The proportion of caches was significantly higher in shrubs with high safety cover. The adaptive significance of this foraging behaviour could be a competitive tactic for the rapid sequestering of food from a rich and ephemeral source. Such behaviour would reflect predation risk, which constitutes an important foraging cost in deserts, and could also influence plant community dynamics.     

Locomotion and Escape Modes in Rodents of the Monte Desert (Argentina)

Modes of locomotion and escape tactics are attributes that affect the structure of animal communities, promoting exploitation of different microhabitats and the coexistence of different species. Bipedal locomotion is considered to be more effective than a quadrupedal gait in escaping attacks by predators because it allows for higher speed, a faster response to attack, sudden changes of direction and better detection of aerial raptors. The aim of this study was to determine the type of locomotion used at the moment of escape by three rodent species of the Monte desert –Eligmodontia typus, Akodon molinae and Graomys griseoflavus. The study was carried out in three plant communities of the Ñacuñán Reserve (Mendoza). All three species showed differences in both mode of escape and locomotory pattern. Graomys griseoflavus exhibited the highest proportion of escapes using quadrupedal saltation. The mode of locomotion employed by E. typus varied according to the type of plant communities it inhabited. Those occurring at open sites (Medanal community) exhibited a greater propensity to jump during escapes than those from more sheltered habitats (Algarrobal community). Akodon molinae relied primarily on a quadrupedal gait when fleeing from predators, which would explain its greater dependence on plant cover. Therefore, the morphological and behavioural characteristics of these species are related to their mode of locomotion and the strategies they employ to diminish the risk of predation.     

Phylogenetic relationships among species of the Neotropical genus Graomys (Rodentia: Cricetidae): contrasting patterns of skull morphometric variation and genetic divergence

Subtle differences of external traits characterize species of rodents in the Neotropical genus Graomys. On the other hand, the species differ markedly in chromosome number. In the present study, we evaluate the possible evolutionary forces involved in the evolution of the genus by assessing the degree of intra‐ and interspecific genetic and morphological variation. A phylogenetic analysis demonstrates the existence of at least three species with high levels of genetic distance (10%), which diverged between 1 and 1.5 Mya. Neither Graomys griseoflavus, nor Graomys chacoensis present marked phylogeographical structure. Regarding morphological characters, these species show shape differences in the skull that could be attributable to differences in the local conditions they inhabit, being more marked in G. griseoflavus than in G. chacoensis. The skull shape of G. chacoensis could have evolved under genetic drift, whereas evidence reported in the present study indicates that this character could be under selective pressures in G. griseoflavus. Reconstruction of the ancestral area suggests that G. griseoflavus originated in the central Monte desert, whereas G. chacoensis originated in the Chaco ecoregion surrounding the austral extreme of the Yungas rainforest. Subsequently, both species would have undergone demographic and geographical expansions almost simultaneously, starting approximately 150 000–175 000 years ago. The complex evolutionary history of the genus could be partly explained by the decoupling of morphological, karyological and molecular traits.     

秦岭南北坡森林鼠类对板栗和锐齿栎种子扩散的影响

森林鼠类的种子贮藏行为对植物的扩散及更新会产生积极的影响。2012和2013年秋季,分别在秦岭北坡的周至国家级自然保护区和南坡的佛坪国家级自然保护区内,调查了森林鼠类对板栗(Castanea mollissima)和锐齿栎(Quercus aliena)种子的取食和扩散差异。结果显示:1)秦岭南北坡的环境因素,特别是植被因素,对鼠类扩散板栗和锐齿栎种子具有重要的影响。南坡较为丰富的壳斗科植被种类,导致2种种子在南坡存留时间均长于北坡,而北坡的扩散取食和丢失率均高于南坡。2)种子特征影响鼠类的取食或贮藏偏好。由于较高的蛋白、脂肪等营养含量,鼠类更喜好取食或搬运贮藏板栗种子。然而,低营养但高丹宁含量的锐齿栎种子仍然被鼠类大量贮藏。3)2种种子在南北坡的扩散历程在两个年份间有很大差异,在食物相对匮乏的年份(2012年),种子被扩散的速度更快且丢失的比率更高。这种差异反映了种子大小年现象对森林鼠类取食和贮藏策略的影响。4)无论在秦岭南坡还是北坡,营养价值含量(如蛋白和脂肪)较高的板栗种子的取食和贮藏距离都明显大于营养价值含量较低的锐齿栎种子,这与最优贮藏空间分布模型的预测一致。     

Geographic distribution and phenetic skull variation in two close species of Graomys (Rodentia, Cricetidae, Sigmodontinae)

The interspecific differentiation of South American rodents of the genus Graomys was assayed at ecological and morphometric levels in two species. At the ecological level, niche modelling was used. At the morphometric level, the hypothesis that the size and shape of the skull vary with the geographic location was tested using geometric morphometrics by assessing the extent and spatial distribution of phenotypic skull variation within and among two species, Graomys griseoflavus and Graomys chacoensis. Our results of niche modelling indicate the spatial differentiation between the two species, with G. chacoensis inhabiting preferably the Chaco ecoregion and G. griseoflavus inhabiting mainly the Monte ecoregion. In multiple linear regressions, approximately 20% of the skull size variation is explained by latitude, altitude, and temperature seasonality. The partial least square analysis reveals strong correlation between shape and environmental variables, mainly with latitude, annual mean temperature, and annual precipitation. Discrimination between G. griseoflavus and G. chacoensis was highly reliable when using geometric morphometric tools. These results permit us to elucidate some evolutionary processes that have occurred in these species.     

啮齿动物的分散贮食行为

食物贮藏是许多动物重要的适应性行为,分散贮藏的食物以植物种子为主。每个贮藏点贮藏数量不等的食物项目。啮齿动物分散贮藏食物之后,可降低食物被其他个体获取的机率,提高对食物资源的控制能力,最终有利于自身的生存和繁殖成功。植物种子被贮藏之后,可减少非贮食鼠类对种子的取食。同时,合适的微生境和埋藏有利于种子萌发、幼苗建成和植物的更新;使植物的分布区得以扩展。探讨啮齿动物的分散贮食行为,能够更好地理解食物贮藏在啮齿动物生活史中的作用,进一步认识鼠类和植物的相互关系以及不同啮齿动物在群落形成中的潜在作用。本综述了啮齿动物分散贮食的研究进展,并提出今后工作中的几点建议。     

Food hoarding behaviour of large field mouseApodemus peninsulae

An important behavioural adaptation for animal species with variable or unpredictable food availability is storing food. Food availability for large field mouseApodemus peninsulae (Thomas, 1907) is not reliable. We conducted a series of tests with the large field mouse to determine food hoarding behaviour, response when their hoarded food was removed, and whether perishable foods were treated different than non perishable foods. The study was conducted in four semi-natural enclosures (4 × 3 × 1 m), established on the Donglingshan Mountain near Beijing, China. Thirteen large field mice were placed in enclosures and offered wild apricotPrunus armeniaca seeds and Liaodong oakQuercus liaotungensis acorns. Our results indicated that although large field mice hoarded seeds in larder and scatter patterns, they more frequently exhibited larder hoarding. Liadong oak acorns were generally consumed near the feeder, whereas apricot seeds were more frequently transported to the nest box. Only apricot seeds were scattered among hoard sites. When seeds were removed from hoarding sites the mice responded by taking increased amounts of seeds to their nest for larder and scatter hoarding. Hoarding sites were not randomly distributed throughout the enclosure.     

鼠类对栓皮栎和锥栗种子的贮藏:验证高单宁假说

种子中的单宁影响鼠类的取食和贮藏策略.高单宁假说认为鼠类倾向于优先贮藏单宁含量高的种子、取食单宁含量低的种子.同域分布的鼠类对种子的取食和贮藏选择是否符合高单宁假说的预测尚缺乏足够的实验证据.本研究通过围栏实验研究了四川都江堰地区亚热带常绿阔叶林中的小泡巨鼠(Leopoldamyys edwardsi)、针毛鼠(Niv...     

森林鼠类对秦岭南坡3种壳斗科植物种子扩散的影响

种子作为森林鼠类的主要食物来源,它们的扩散和更新很大程度上依赖于鼠类的传播。在鼠类扩散种子的过程中,种子特征和食物相对丰富度是影响鼠类对种子进行何种选择策略的重要因素。2011—2012年的8—12月,采用塑料片标记法在秦岭南坡的佛坪国家级自然保护区内调查了森林鼠类对同域分布的3种壳斗科植物(锐齿槲栎Quercus aliena var.acuteserrata、栓皮栎Q.variabilis和短柄枹栎Q.serrata var.brevipetiolata)种子的扩散差异。结果表明:(1)鼠类倾向于贮藏营养价值较大的栓皮栎种子,并且其贮藏距离也最远(2011:1.52 m,2012:4.03 m),3种种子在食物相对丰富度较低年份被贮藏的距离均较远。(2)在食物相对丰富度较高的年份(2011),种子的消耗速率较慢,在种子释放10 d后种子释放点仍有67.33%的种子,贮藏量较高,至实验结束仍有29.67%的种子被贮藏。在食物相对丰富度较低的年份(2012),种子消耗速率较快,在种子释放后10 d内所有种子均被取食或搬离种子释放点,贮藏量较低,至实验结束仅有3.83%的种子仍被贮藏。(3)虽然栓皮栎种子的贮藏量最大,被贮藏后的存留量也最大,但其在实验地的分布却较小,说明种子扩散仅是植物分布与存活的第一步。以上结果表明,鼠类倾向于贮藏营养价值高的种子。在食物相对丰富度较高的年份会更多的贮藏种子,但种子被贮藏的距离较近,在食物相对丰富度较低的年份会更多的取食种子。     

Environmental determinants of the small mammal assemblage in an agroecosystem of central Argentina: The role of Calomys musculinus

Agricultural intensification in the central region of Argentina has been accompanied by rodent assemblage changes, involving an increase in Calomys species densities. In particular, Calomys musculinus, the main reservoir of Junín virus (etiological agent of the Argentine Haemorrhagic Fever, AHF) selects field borders over crop-fields. Borders represent relatively-stable habitats within agroecosystems, otherwise highly human modified landscapes. In this article, we assessed the effect of environmental variables on rodent species occurrence and assemblage in the field borders of a pampean agroecosystem. Small rodent occurrence was examined for variation according to vegetation species composition, structure and productivity, using canonical ordination techniques. In a total of 72 crop-field borders of Córdoba province, in spring, summer and autumn (2005-2006), we captured 1041 rodents of 8 different species. Akodon azarae, Calomys venustus and C. musculinus were the dominant species of the assemblage, with the first two associated one another, while C. musculinus tended to be related to different environmental variables. We showed that rodent species associations were mediated by resources that changed seasonally, such as vegetation cover. Also, the strength and “sign” of the association between species seemed to be a consequence of different habitat preferences and activity patterns. Finally, the intra-annual population cycle seemed to influence the relation between species and habitat structure and, possibly, inter-specific competition for resources. Therefore, we suggest that less generalist species of the rodent assemblage, well adapted to linear habitats, may limit C. musculinus occurrence throughout the agroecosystem by habitat and spatial competition. Any action aimed to control AHF, and therefore C. musculinus population density, should exclude negative effects on coexisting species.     

Effects of seed abundance on seed scatter-hoarding of Edward’s rat (<Emphasis Type="Italic">Leopoldamys edwardsi</Emphasis> Muridae) at the individual level

Mast seeding is a common phenomenon, and has important effects on seed dispersal and hoarding by animals. At population level, the predator satiation hypothesis proposes that the satiating effect of a large amount of seeds on a relatively small number of predators benefits seed survival in mast-seeding years. However, the effect of mast seeding on the scatter-hoarding of rodents at the individual level is largely unknown. In this study, we investigated the effects of seed abundance (by simulating mast seeding and non-mast seeding) on the removal, consumption and scatter-hoarding of seeds of Camellia oleifera (Theaceae) by Edward’s rat Leopoldamys edwardsi (Muridae) in seminatural enclosures in southwest China. We wanted to test the masting-enhanced hoarding hypothesis, which suggests that rodents tend to scatter-hoard more seeds in mast-seeding years in order to occupy more food resources. Our results indicate that L. edwardsi tended to disperse and scatter-hoard more seeds of C. oleifera per night with increasing seed abundance, and to eat less seeds per night when there was a high level of seed abundance in the enclosure experiments. These results support the masting-enhanced hoarding hypothesis. This capacity of rodents may be an evolutionary adaptation to the mast-seeding phenomenon. Our results suggest that mast seeding benefits forest regeneration not only through the predator satiation effect at the population level, but also through increased hoarding by animals at the individual level. Hongmao Zhang and Jinrui Cheng have contributed equally to this work.     

Spacing Behavior of a Non‐Larder‐Hoarding Tamiasciurus: A Study of Mearns's Squirrels in Xeric Coniferous Forests

In ecosystems with seasonal fluctuations in food supply many species use two strategies to store food: larder hoarding and scatter hoarding. However, because species at different geographic locations may experience distinct environmental conditions, differences in hoarding behavior may occur. Tree squirrels in the genus Tamiasciurus display variation in hoarding behavior. Whereas red (Tamiasciurus hudsonicus) and Douglas's (Tamiasciurus douglasii) squirrels in mesic coniferous forests defend territories centered around larder hoards maintaining non‐overlapping home ranges, red squirrels in deciduous forests defend small scatter‐hoarded caches of cones maintaining overlapping home ranges. As in other rodent species, variation in hoarding behavior appears to influence the spacing behavior of red and Douglas's squirrels. In contrast, Mearns's squirrels (Tamiasciurus mearnsi) in xeric coniferous forests neither rely on larder hoards nor appear to display territorial behavior. Unfortunately, little is known about the ecology of this southernmost Tamiasciurus. Using radiotelemetry, we estimated home‐range size, overlap, and maximum distance traveled from nest to examine the spacing behavior of Mearns's squirrels. Similar to scatter‐hoarding rodents, maximum distance traveled from nest was greater for males during mating season, whereas those of females were similar year round. Although no seasonal differences were detected, male home ranges were three times larger during mating season, whereas those of females were smaller and displayed a minor variation between seasons. Home ranges were overlapped year round but contrary to our expectations, overlap was greater during mating season for both sexes, with no detectable relationship between male home‐range size and the number of females overlapped during mating season. Overall, the results appear to support our hypothesis that in the absence of larder hoards, the spacing behavior of Mearns's squirrels should be different from larder‐hoarding congeners and more similar to scatter‐hoarding rodents.     

Patterns of speciation in two sibling species of Graomys (Rodentia,Cricetidae) based on mtDNA sequences

To increase our understanding of the speciation process occurred in the sibling species Graomys griseoflavus and Graomys centralis, a phylogeographic study was conducted based on sequences of a hypervariable segment of the mtDNA D‐loop region. The resulting haplotype phylogenetic network showed two well‐defined clusters, one for each species. The clusters were connected by two haplotypes from localities that are almost 300 km apart, one situated in the Monte eco‐region and the other, in the Chaco. This result is in agreement with a previous hypothesis about the geographical context in which the cladogenetic process occurred. A divergence time of 0.15–0.28 million years was estimated, which is consistent with a process of recent speciation. An amova test confirmed that at present gene flow between species does not exist. The mismatch distribution analyses suggest that the geographical and demographic expansion undergone by the species is related to the climatic events that occurred in the region during the Quaternary.     

Ignorant seed predators and factors affecting the seed survival of a tropical palm

In addition to acting as seed predators, some terrestrial mammals bury seeds via scatter hoarding. This study system used two permanent plots in examining the interaction between small rodents and the seeds of the palm Astrocaryum mexicanum. We tested how experimental burial, and fruiting status of the parent, distance to the parent, seed size, and microsite characteristics affect the survival of these seeds. Up to 34% of the buried seeds that were exposed only to ignorant rodent foragers (individuals not responsible for burial) survived. In comparison, less than 1% of seeds buried by scatter hoarding rodents survived in previous studies, a percentage that is comparable to the low survival of unburied seeds in this study (<2%). Although unburied seeds had very low survival, increasing distance and/or seed density positively affected survival of unburied seeds. Distance to parent had no effect on buried seed survival.
Buried seed survival was most strongly and significantly determined by the fruiting status of the trees under which they occurred. Seeds experienced significantly greater predation if buried under “parent” trees that fruited during the experiment. Buried seed survival was also negatively affected by germination, as germination may signal the presence of a seed to foraging rodents. There was some indication of a positive effect of tree density on seed survival between the two plots, whereas differences in rodent abundance appear to have no effect on seed survival. Seed size and microsite characteristics had no significant effect on buried seed survival, likely due to the greater proportional effects of other factors and the longevity of A. mexicanum seeds. The results of this study were used to generate a hypothetical causal network showing how comparatively low recovery of buried seeds by ignorant foragers – combined with processes determining the removal of scatter hoarding foragers from their scattered seed caches – may affect seedling recruitment in A. mexicanum.     

Tropical rodents change rapidly germinating seeds into long-term food supplies

Seed‐hoarding vertebrates may survive yearly periods of food scarcity by storing seeds during the preceding fruiting season. It is poorly understood why rodents creating long‐term reserves, especially those in the tropics, incorporate seeds from plant species that germinate rapidly and hence seem unsuitable for long‐term storage. We carried out a series of experiments to understand why red acouchies (Myoprocta exilis) scatter‐hoard Carapa procera (Meliaceae) seeds, which lack dormancy and germinate rapidly. Hypotheses tested were: (1) even germinated seeds are still significant long‐term energy reserves for acouchies, (2) acouchies use the seeds only as short‐term supplies, and (3) acouchies manipulate the seeds to slow down germination. The first two hypotheses were not supported; seed reserves were rapidly depleted during experimental planting, and acouchies did use seeds for long‐term storage. We did find support for the third hypothesis. Acouchies intervened in germination by removing the protruding radicle and epicotyl after which they re‐cached seeds. Pruning stopped further seedling development, yet the pruned seeds did not decay. The cotyledons apparently stayed alive and physiologically active as “zombie seeds” that only formed undifferentiated calli. Pruned seeds were suitable for long‐term storage, with negligible loss of endosperm over time. Pruning was most effective after sprouting of the epicotyl, and germinating seeds were most susceptible to pruning during two weeks upon emergence. Acouchies actively managed their food supplies and must continuously survey for germinating seeds to timely intervene in seed reserve depletion, within the brief period of seedling emergence. We suggest that the trees use the rodents to achieve seed dispersal, and gain from imperfect intervention in germination by the rodents. Because scatter‐hoarding rodents and large‐seeded plant species with similar germination co‐occur in tropical forests world‐wide, it is plausible that the phenomenon of seed pruning to preserve seeds is more general than currently appreciated.     

Loss of nucleolar organizer regions during chromosomal evolution in the South American cricetid Graomys griseoflavus

Graomys griseoflavus is a South American phyllotine rodent having a remarkable Robertsonian polymorphism which may have produced reproductive isolation between 2n=42–41 and 2n=38–34 karyomorphs. Analysis of nucleolar organizer region (NOR) locations both by silver staining (Ag-NOR) and in situ hybridization revealed that 2n=42 individuals exhibit highly variable Ag-NOR patterns, while specimens of the 2n=38–34 karyomorphic group showed a single Ag-NOR pattern. The latter animals underwent two NOR deletions in reference to the 2n=42 karyomorphs, one of which would be the consequence of a Robertsonian fusion and the other would be produced by the unequal crossing-over mechanism. The differential NOR homogenization supports the hypothesis that G. griseoflavus karyomorphs are evolving separately towards the acquisition of separate species status.