Origin of caulinary ant domatia and timing of their onset in plant ontogeny: evolution of a key trait in horizontally transmitted ant-plant symbioses

Many ant plants possess caulinary domatia, hollow and usually swollen stems. What are the evolutionary origins of this key trait of ant‐plant symbioses? In a single lineage, myrmecophytes often differ in the timing of the first appearance of domatia. What processes have led to diversification in the timing of expression of domatia in ontogeny? We suggest that an approach based on the analysis of leaf‐ stem size correlations, that appear general in trees, can supply answers to both these questions. Traits associated with increased primary diameter of twigs may have facilitated the evolution of domatia. Among lineages, differences in stem diameter may help to explain why domatia appeared in some, and not in others. Within species, because twig primary diameter increases over plant ontogeny, initially ants may have colonized only plants at later stages of development, whose twigs had reached a minimum size. We thus postulate that expression of domatia later in development is the primitive condition in lineages with domatia, and that increasing specialization of ants and plants enhanced both the probability of establishment and ant protection, favouring precocity of onset of domatia and other myrmccophytic characters. In the language of heterochrony, these characters are affected by prc‐displacement.     

Leaf domatia: carbon‐limited indirect defence?

Plant‐based defence mutualisms utilize plant morphology to reduce the performance of plant parasites through their natural enemies. Leaf domatia primarily occur in the axials of secondary veins and are often inhabited by microbivorous and predaceous mites which often increase plant growth rates and reproductive success by controlling plant pests. Our study investigated if domatia investment is limited by plant primary productivity. To our knowledge no studies have tested if foliar domatia are resource‐limited. We tested our hypothesis using the genus Coprosma (Rubiaceae), conducting correlative field surveys and manipulative experiments measuring domatia production in new leaves along temperature, nutrient and irradiance gradients. Field surveys indicated a strong positive association between leaf area, the number of secondary veins, and domatia per leaf. The number of potential sites for domatia is underutilised, with leaves on selected Coprosma species having on average 47 to 72% of the ‘maximum’ number of available sites where domatia could occur. Foliar carbon was positively associated with domatia investment. Coprosma plants held under elevated night‐time temperatures showed a 34–91% decrease in daily carbon gain, a 38% decrease in domatia per leaf mass, and a positive relationship between domatia investment and integrated daily carbon gain. Under irradiance and nutrient stress, our data indicated evidence of a positive relationship between domatia investment and foliar carbon. We found a significant negative association between relative investment in domatia produced and investment in new leaf biomass. Our findings suggest investment in foliar domatia is limited by primary productivity. We propose that domatia are discretionary goods and not intrinsic structures produced automatically on leaves that mites utilize. We suggest that plants have the ability to regulate domatia formation during leaf ontogeny, with investment controlled by resource availability and some intrinsic allocation mechanism to defence.     

Permanent Genetic Resources added to Molecular Ecology Resources Database 1 June 2010 - 31 July 2010

This article documents the addition of 205 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Bagassa guianensis, Bulweria bulwerii, Camelus bactrianus, Chaenogobius annularis, Creontiades dilutus, Diachasmimorpha tryoni, Dioscorea alata, Euhrychiopsis lecontei, Gmelina arborea, Haliotis discus hannai, Hirtella physophora, Melanaphis sacchari, Munida isos, Thaumastocoris peregrinus and Tuberolachnus salignus. These loci were cross-tested on the following species: Halobaena caerulea, Procellaria aequinoctialis, Oceanodroma monteiroi, Camelus ferus, Creontiades pacificus, Dioscorea rotundata, Dioscorea praehensilis, Dioscorea abyssinica, Dioscorea nummularia, Dioscorea transversa, Dioscorea esculenta, Dioscorea pentaphylla, Dioscorea trifida, Hirtella bicornis, Hirtella glandulosa, Licania alba, Licania canescens, Licania membranaceae, Couepia guianensis and 7 undescribed Thaumastocoris species.     

How leaf domatia and induced plant resistance affect herbivores, natural enemies and plant performance

Predators and plant resistance may act together to control herbivorous arthropod populations or antagonistically, which would reduce the control of pest populations. In a field experiment we enhanced predation by adding simulated leaf domatia to plants. Leaf domatia are small structures that often harbor predaceous arthropods that are potentially beneficial to the plant. We also manipulated host plant quality by inducing resistance with controlled, early season exposure of seedlings to spider mite herbivory.
Our manipulations had profound consequences for the natural community of arthropods that inhabited the plants. Leaf domatia had a direct positive effect on abundances of two species of bugs and one species of thrips, all of which are largely predators of herbivores. On leaves with domatia, each of the predators was found inside the domatia two to three times more often than outside the domatia. Eggs of predaceous bugs inside leaf domatia were protected from parasitism compared to eggs outside the domatia. The positive effects of leaf domatia on predator abundances were associated with reduced populations of herbivorous spider mites, aphids, and whiteflies. Plants with experimental leaf domatia showed significantly enhanced reproductive performance.
Induced resistance also affected the community of arthropods. Of the abundant predators, all of which also fed on the plant, only minute pirate bugs were negatively affected by induced resistance. Populations of herbivorous spider mites and whiteflies were directly and negatively affected by induction. In contrast, aphid populations were higher on plants with induced resistance compared to uninduced plants. Effects of induced resistance and domatia were additive for each of the predators and for aphids. However, spider mite and whitefly populations were not suppressed further by employing both induced resistance and domatia compared to each strategy alone. Our manipulations suggest that plant defense strategies can have positive effects on some species and negative effects on others. Negative effects of “resistance traits” on predators and positive effects on some herbivores may reduce the benefits of constitutive expression of resistance traits and may favor inducible defense strategies. Multiple plant strategies such as inducible resistance and morphological traits that aid in the recruitment of predators of herbivores may act together to maximize plant defenses, although they may also be redundant and not act additively.     

Leaf domatia in Korean plants: floristics,frequency, and biogeography

Leaf domatia, specialized structures on the undersides of leaves, appear to promote mutualism between plants and those mites that protect leaves from pathogenic fungi and small herbivorous arthropods. Their occurrence was surveyed on 425 plant species (368 native species and 57 species introduced from other regions of northeastern Asia), comprising 177 genera and 59 families of woody Dicotyledonae in the Korean flora. Domatia, primarily of tuft or pocket forms (84% of species), were present in vein axils on leaves of 152 species (36%) within 66 genera (37%) and 39 families (66%). Overall, we report leaf domatia in nine new families and 25 additional genera. Mites, primarily from families or suborders (e.g., Acaridida, Phytoseiidae, Tydeidae) in which arboreal representatives are primarily fungivorous or predaceous, were found in domatia on leaves of 78% of all species sampled. Domatia frequency depended upon both growth form and habit of species. They were especially common among tree species (55%), but less so on shrubs (20%) and woody vines (22%). Domatia were much more frequent on species of deciduous plants (40% of those sampled) than on evergreen species, of which only 10% had leaf domatia. This difference was consistent across a number of local deciduous and broadleaf evergreen forests in South Korea. The high frequency of leaf domatia in this survey indicates that plant-mite mutualism may be widespread in Korean plant communities. The floristic affinities of plants with domatia in Korea to those in other regions of East Asia, eastern North America, and Europe suggest that these plant-mite associations characterize the temperate broadleaf deciduous forest biome in the Northern Hemisphere.     

Research on Bioecological Characteristics of Suaeda physophora and Its Community at the Hutubi Cattle Farm Area of Xinjiang,China

Suaeda physophora was distributed on the saline soil with a salt contents 3.0%～ 6.0% in the surface layer (0420 cm underground). The plant height was 45～60 cm and the average length of the one-year twig was 12 cm. The succulent leave was strip shaped. The well developed lateral roots was distributed in the deeper soil (EOb 60 cra) with decreased salt contents and increased water content. The multiregression model for individual plant's aboveground biomass was: Y = 312. 00 + 3.44X1 + 4. 85X2 - 2.16X3 (Xl, length; X2, width: X3, height). The contents of Na, S and K in leave of S. physophora were very high. That of Na was 91255 μg · g-1. The element contents varied in the different parts of plant. K, Na, Mg, S and P contents were the highest respectively in the leaf and ear of flower, but they were the lowest in the old twig. Total salt content of water extracts from tender twig and leaf was 23.17%, being more than in ear of flower and old twig. The element and salt contents varied in different seasons of plant growth. The S. physophora community was a formation on the succulent halophytic dwarf sub-shrub desert. Nine associations were recorded at this area. The coverage of community was 6 % ~25 %.     

Comparative morphology and diet of young cichlids in the dammed Sinnamary river, French Guiana, South America

The growth of most mensural characters of Krobia guianensis and Crenicichla saxatilis during early development was explained by a split regression indicating inflection in allometry at specific standard lengths. Double-centred PCA revealed morphological transformations during ontogeny mostly under the influence of the maximum body depth and the maximum caudal peduncle width, the area of the caudal fin and the horizontal diameter of the eye contributing also, but to a lesser extent. Young K. guianensis switched to larger prey at the end of the period when the growth of most of their studied mensural characters demonstrated an inflection, but young C. saxatilis changed their diet at a much smaller size than that at which an inflection occurred. However, in the lower reservoir sites, most young juveniles of K. guianensis and C. saxatilis did not switch to larger items during their ontogeny and micro-crustaceans occurred more frequently in their diet. It is hypothesized that the low net energy gained when eating such small prey may explain why the young of both species were thinner at these sites than in their undisturbed habitats. If food resources of young cichlids do not improve in the Petit-Saut reservoir, it is hypothesized that these species will develop stunted populations there.     

Do leaf domatia mediate a plant–mite mutualism? An experimental test of the effects on predators and herbivores

1. Leaf domatia are tiny structures in leaf vein axils that are widespread among plant taxa and have been described to be typically inhabited by predatory and fungivorous mites. The mutualism hypothesis for the function of leaf domatia predicts that predatory and/or fungivorous mites benefit from having a favourable place to take refuge and reproduce and that plants benefit indirectly from reduced herbivory and/or pathogen attack.
2. The effect of leaf domatia on populations of predatory and herbivorous mites was examined for avocado, Persea americana . In separate experiments, domatia were added to leaves of a variety of avocado plants lacking domatia (Hass) and domatia were blocked on a domatia-bearing variety (Toro Canyon).
3. In two out of the five experiments conducted, domatia-bearing plants had significantly higher numbers of predatory mites compared with controls. Although herbivore numbers were consistently lower on plants with domatia than on plants without domatia, in no case did the presence of leaf domatia result in a statistically significant decrease in herbivorous mite populations.
4. These results suggest that domatia may frequently benefit predatory mites, however, indirect effects on herbivorous mites may not commonly exist or may be too difficult to detect.     

A comparative study on the anatomy and development of different shapes of domatia in Cinnamomum camphora (Lauraceae)

BACKGROUND AND AIMS: Domatia are small organs usually found in the axils of major veins on the underside of leaves and, although they have received wide attention from ecologists, few detailed reports exist on their anatomy or development. This study is focused on the domatia of Cinnamomum camphora (Lauraceae) and is the first comparative study on the anatomy and development of the different shapes of domatia within a single plant. METHODS: Four types of domatia in C. camphora leaves were observed on paraffin sections under a microscope. KEY RESULTS: The domatia consisted of six histological parts: the upper epidermis, the upper mesophyll tissue, spongy tissue, the lower mesophyll tissue, the tissue filling the rim opening, and the lower epidermis. They differed from the non-domatial lamina mainly in the cell structure of the upper and lower mesophyll tissue and the rim tissue. Differences in domatium shapes were mainly associated with differences in the structure of the upper mesophyll and in the number and size of the rim tissue cells. Differences in the development of domatium types were observed in terms of initiation timing, differentiation of the upper mesophyll cells and degree of rim tissue development. CONCLUSIONS: In domatia, active anticlinal division in the lower mesophyll cells, as compared with the upper mesophyll cells, was coordinated with dynamic growth of rim tissue cells and resulted in cavity formation. The anatomical or developmental differences among the four types of domatia were related to the positions of the domatia within a leaf. In terms of the ecological implications, the major anatomical difference between the domatia used by herbivorous and carnivorous mites was in the development of the rim tissue.     

Leaf domatia and mites on Australasian plants: ecological and evolutionary implications

Leaf domatia, specialized chambers in the vein axils on the underside of leaves of many plant species, have remained an enigma for over a century. In this study we show a strong association between foliar domatia and mites in 37 plant species in Australasia. Overall, mites accounted for 91% of the arthropods observed in domatia. Across all species, a median of 51% of domatia were occupied and 71% of leaves showed mite evidence in domatia. The level of mite association did not depend on domatia type (pit, pouch, pocket, or tuft) or provenance (Papua New Guinea, Queensland, Victoria, or New Zealand). Mite association with domatia commonly varied between plant species, between individuals within species, and between shoots within individuals. The leaf developmental stage probably explains much of the variation in association for many of these species. The presence of a variety of life history stages of mites within domatia indicates that these structures act as shelters for development and reproduction. Furthermore, in 12 of 13 plant species examined, domatia concentrate mites in particular locations on the leaf. Mite taxa that we classify as largely predaceous (e.g. phytoseiids, stigmaeids and tydeids) or fungivorous (e.g. acarids and oribatids) were most common in domatia and dominated the association in 21 of 24 plant species in which the relative abundance of herbivorous, fungivorous and predaceous groups was quantified. We evaluate hypotheses that explain the role of leaf domatia, including non-functional hypotheses (e.g. architectural constraints), physiological function (e.g. gas exchange and water uptake), bacterial symbiosis and antagonistic and mutualistic associations with mites. Our quantitative results confirm anecdotal accounts of mite association with leaf domatia and are most consistent with Lundströem's century-old hypothesis of plant-mite mutualism in which leaf domatia billet predaceous and fungivorous mites that prey on plant enemies. Leaf domatia are widespread among woody angiosperms and abundant in many temperate and tropical regions of Australasia. Mites, an ancient group of arthropods whose diversity and abundance parallels that of insects, are likely to be important selective agents on terrestrial plants. Our results (1) indicate that mite-domatia association represents a relationship of comparable scope to plant-ant associations mediated by specialized plant structures such as extrafloral nectaries, food bodies and specialized domatia; (2) suggest that sociality is not a necessary prerequisite for widespread and diverse mutualisms between arthropods and plants; and, (3) extend the diversity of organisms that produce specialized mite ‘houses’ from lizards, and wasps and bees to woody angiosperms.     

Leaf domatia and foliar mite abundance in broadleaf deciduous forest of north Asia

Plant morphology may be shaped, in part, by the third trophic level. Leaf domatia, minute enclosures usually in vein axils on the leaf underside, may provide the basis for protective mutualism between plants and mites. Domatia are particularly frequent among species of trees, shrubs, and vines in the temperate broadleaf deciduous forests in north Asia where they may be important in determining the distribution and abundance of mites in the forest canopy. In lowland and montane broadleaf deciduous forests at Kwangn;akung and Chumbongsan in Korea, we found that approximately half of all woody species in all forest strata, including many dominant trees, have leaf domatia. Pooling across 24 plant species at the two sites, mites occupied a mode of 60% (range 20-100%) of domatia and used them for shelter, egg-laying, and development. On average, 70% of all active mites and 85% of mite eggs on leaves were found in domatia; over three-quarters of these were potentially beneficial to their hosts. Further, mite abundance and reproduction (expressed as the proportion of mites at the egg stage) were significantly greater on leaves of species with domatia than those without domatia in both forests. Effects of domatia on mite abundance were significant only for predaceous and fungivorous mite taxa; herbivore numbers did not differ significantly between leaves of species with and without domatia. Comparable patterns in broadleaf deciduous forest in North America and other biogeographic regions suggest that the effect of leaf domatia on foliar mite abundance is general. These results are consistent with several predictions of mutualism between plants and mites, and indicate that protective mutualisms may be frequent in the temperate zone.     

Comparison between the anatomical and morphological structure of leaf blades and foliar domatia in the ant-plant Hirtella physophora (Chrysobalanaceae)

Background and Aims: Myrmecophytes, or ant-plants, are characterized by their abilityto shelter colonies of some ant species in hollow structures,or ant-domatia, that are often formed by hypertrophy of theinternal tissue at specific locations (i.e. trunk, branches,thorns and leaf pouches). In Hirtella physophora (Chrysobalanaceae),the focal species of this study, the ant-domatia consist ofleaf pouches formed when the leaf rolls over onto itself tocreate two spheres at the base of the blade. Methods: The morphological and anatomical changes through which foliarant-domatia developed from the laminas are studied for the firsttime by using fresh and fixed mature leaves from the same H.physophora individuals. Key results: Ant-domatia were characterized by larger extra-floral nectaries,longer stomatal apertures and lower stomatal density. The anatomicalstructure of the domatia differed in the parenchymatous tissuewhere palisade and spongy parenchyma were indistinct; chloroplastdensity was lower and lignified sclerenchymal fibres were morenumerous compared with the lamina. In addition, the domatiawere thicker than the lamina, largely because the parenchymatousand epidermal cells were enlarged. Conclusions: Herein, the morphological and anatomical changes that permitfoliar ant-domatia to be defined as a specialized leaf structureare highlighted. Similarities as well as structural modificationsin the foliar ant-domatia compared with the lamina are discussedfrom botanical, functional and mutualistic points of view. Theseresults are also important to understanding the reciprocal evolutionarychanges in traits and, thus, the coevolutionary processes occurringin insect–plant mutualisms.     

Evolution of myrmecophytism in western Malesian Macaranga (Euphorbiaceae)

Plants inhabited by ants (myrmecophytes) have evolved in a diversity of tropical plant lineages. Macaranga includes approximately 300 paleotropical tree species; in western Malesia there are 26 myrmecophytic species that vary in morphological specializations for ant association. The origin and diversification of myrmecophytism in Macaranga was investigated using phylogenetic analyses of morphological and nuclear ITS DNA characters and studies of character evolution. Despite low ITS variation, the combined analysis resulted in a well-supported hypothesis of relationships. Mapping myrmecophytism on all most parsimonious trees resulting from the combined analysis indicated that the trait evolved independently between two and four times and was lost between one and three times (five changes). This hypothesis was robust when tested against trees constrained to have three or fewer evolutionary transformations, although increased taxon sampling for the ITS analysis is required to confirm this. Mapping morphological traits on the phylogeny indicated that myrmecophytism was not homologous among lineages; each independent origin involved a suite of different specializations for ant-plant association. There was no evidence that myrmecophytic traits underwent sequential change through evolution; self-hollowing domatia evolved independently from ant-excavated domatia, and different food-body production types evolved in different lineages. The multiple origins of myrmecophytism in Macaranga were restricted to one small, exclusively western Malesian lineage of an otherwise large and nonmyrmecophytic genus. Although the evolution of aggregated food-body production and the formation of domatia coincided with the evolution of myrmecophytism in all cases, several morphological, ecological, and biogeographic factors appear to have facilitated and constrained this radiation of ant-plants.     

Mechanisms driving the specificity of a myrmecophyte–ant association

In the understory of pristine Guianese forests, the myrmecophyte Hirtella physophora almost exclusively shelters colonies of the plant-ant Allomerus decemarticulatus in its leaf pouches. We experimentally tested three non-mutually exclusive hypotheses concerning phenomena that can determine the species specificity of this association throughout the foundation stage of the colonies: (1) interspecific competition results in the overwhelming presence of A. decemarticulatus queens or incipient colonies; (2) exclusion filters prevent other ant species from entering the leaf pouches; and (3) host-recognition influences the choice of founding queens, especially A. decemarticulatus . Neither interspecific competition, nor the purported exclusion filters that we examined play a major role in maintaining the specificity of this association. Unexpectedly, the plant trichomes lining the domatia appear to serve as construction material during claustral foundation rather than as a filter. Finally, A. decemarticulatus queens are able to identify their host plant from a distance through chemical and/or visual cues, which is rarely demonstrated in studies on obligatory ant–plant associations. We discuss the possibility that this specific host-recognition ability could participate in shaping a compartmentalized plant-ant community where direct competition between ant symbionts is limited.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 90–97.     

Geographical genetic structuring and phenotypic variation in the Vellozia hirsuta (Velloziaceae) ochlospecies complex

? Premise of the study: Vellozia hirsuta forms a complex presenting wide morphological and anatomical variation, resulting in five specific names and 14 morpho-anatomical patterns occurring in disjunct populations. We carried out a phylogeographical study to investigate the existence of correlation among the genetic and morphological patterns within this complex, and to determine whether it is composed of various species or should be treated as an ochlospecies, a species having widely polymorphic and weakly polytypic complex variation, with morphological characteristics varying independently. ? Methods: We carried out phylogeographical analyses using cpDNA rpl32F-trnL intergenic region. ? Key results: We found 20 haplotypes in 23 populations sampled. The populations are genetically structured (Φ(ST) = 0.818) into four phylogeographical groups demonstrating geographical structuring but with no correlation with morpho-anatomical patterns. Our analyses do not support recognizing any of the species now synonymized under Vellozia hirsuta. The northern populations were the most genetically differentiated and could be considered a distinct taxon, as they are also morphologically different. ? Conclusions: It is recommended that Vellozia hirsuta be considered a single enormously variable species. The patterns of variation within V. hirsuta probably are related to climatic changes that occurred during the Pleistocene Epoch in tropical Brazil when reductions in forest cover favored the expansion of V. hirsuta populations into extensive lowland areas. The expansion of forest cover at the end of the glaciations would have again restricted the occurrence of campos rupestres vegetation to high elevations, which constitute the current centers of diversity of this species.     

Are ontogenetic shifts in foliar structure and resource acquisition spatially conditioned in tank‐bromeliads?

The phenotypic plasticity of plants has been explored as a function of either ontogeny (apparent plasticity) or environment (adaptive plasticity), although few studies have analyzed these factors together. In the present study, we take advantage of the dispersal of Aechmea mertensii bromeliads by Camponotus femoratus or Pachycondyla goeldii ants in shaded and sunny environments, respectively, to quantify ontogenetic changes in morphological, foliar, and functional traits, and to analyze ontogenetic and ant species effects on 14 traits. Most of the morphological (plant height, number of leaves), foliar (leaf thickness, leaf mass area, total water content, trichome density), and functional (leaf δ¹³C) traits differed as a function of ontogeny. Conversely, only leaf δ¹⁵N showed an adaptive phenotypic plasticity. On the other hand, plant width, tank width, longest leaf length, stomatal density, and leaf C concentration showed an adaptation to local environment with ontogeny. The exception was leaf N concentration, which showed no trend at all. Aechmea mertensii did not show an abrupt morphological modification such as in heteroblastic bromeliads, although it was characterized by strong, size‐related functional modifications for CO₂ acquisition. The adaptive phenotypic variation found between the two ant species indicates the spatially conditioned plasticity of A. mertensii in the context of insect‐assisted dispersal. However, ant‐mediated effects on phenotypic plasticity in A. mertensii are not obvious because ant species and light environment are confounding variables. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175 , 299–312.     

Leaf domatia mediate mutualism between mites and a tropical tree

Although associations between mites and leaf domatia have been widely reported, their consequences for plants, especially for natural tree populations, particularly in the tropics, are largely unknown. In experiments with paired Cupania vernalis (Sapindaceae) saplings in a semi-deciduous forest in south-east Brazil, we blocked leaf domatia to examine their effect: (1) on mites and other arthropods, and (2) on damage caused by fungi and herbivorous arthropods. In general, plants with resin-blocked domatia had fewer predaceous mites on leaves than control plants with unaltered domatia, but the total abundances of fungivorous and of phytophagous mites remained unchanged. However, phytophagous eriophyid mites, the most numerous inhabitants of domatia, decreased on leaf surfaces with the blocking treatment. In a second experiment, treated plants lacking functional domatia developed significantly greater numbers and areas of chlorosis, apparently due to increased eriophyid attacks, whereas fungal attack, epiphyll abundance and leaf-area loss were unaffected. This seems to be the first experimental study to demonstrate that leaf domatia can benefit plants against herbivory in a natural system. The possible stabilizing effect of leaf domatia on predator-prey interactions is discussed.     

OCCURRENCE OF PREDATORY AND FUNGIVOROUS MITES IN LEAF DOMATIA

Domatia are small invaginations and hair tufts usually found at vein junctions on the undersides of leaves in many woody dicots. Domatia of 32 plant species (of worldwide origin from 18 families) growing in California, Hawaii, and Costa Rica were examined for mites. Domatia of 31 of 32 (97%) of these plants contained mites, and 24 of 32 (75%) contained mite eggs. Mites were found within the domatia of 48% of the sampled leaves. The domatia of 26 of 31 (84%) plants had mite species considered beneficial (primarily in the families Phytoseiidae and Tydeidae, but also Bdellidae, Cheyletidae and Stigmaeidae), while 6 of 31 (19%) had mite species considered harmful (Tenuipalpidae and Eriophyidae). Based on these findings (and in part upon Lundström's 1887 domatia theory), we hypothesize the existence of a widespread facultative mutualism between plants with leaf domatia and beneficial mites: leaf domatia serve as shelters and nurseries for mites which in turn eat phytophagous arthropods and pathogens using the plants. This proposed mutualism could be of importance to agriculture since domatia are known to occur in some crop plants, including coffee, grape, and walnut.     

Host plant manipulation of natural enemies: leaf domatia protect beneficial mites from insect predators

Acarodomatia are small tufts of hair or invaginations in the leaf surface and are frequently inhabited by several taxa of non-plant-feeding mites. For many years, ecologists have hypothesized that these structures represent a mutualistic association between mites and plants where the mites benefit the plant by reducing densities of phytophagous arthropods and epiphytic microorganisms, and domatia benefit the mite by providing protection from stressful environmental conditions, other predaceous arthropods, or both. We tested these hypothesized benefits of domatia to domatia-inhabiting mites in laboratory and growth chamber experiments. In separate experiments we examined whether domatia on the wild grape, Vitis riparia, provided protection against drying humidity conditions or predaceous arthropods to two species of beneficial mite: the mycophagous species Orthotydeus lambi, and the predaceous species Amblyseius andersoni. For both taxa of beneficial mite, domatia significantly increased mite survivorship in the presence of the predatory bug, Orius insidiosus and the coccinellids Coccinella septempunctata and Harmonia varigata. There was no evidence for a protective effect of domatia with a third species of predatory arthropod, lacewing larvae Chrysoperla rufilabris. In contrast, there was no evidence for either species of beneficial mite that domatia provided any protection against low humidity. Thus in this system the primary mechanism by which domatia benefit beneficial mites is by protecting these organisms from other predatory arthropods on the leaf surface.     

Fossil evidence of evolutionary convergence in juvenile dental morphology and upper canine replacement in sabertooth carnivores

The convergent suite of morphological traits characterizing the mammalian sabertooth ecomorphology is well documented, including modifications of the dental and osteological portions of the masticatory apparatus from a less‐specialized carnivore condition. Equally important is how those specialized adult morphologies developed through ontogeny because previous studies have shown that growing such specialized craniodental traits may require evolutionary modification of growth patterns and tooth replacement mechanisms. Despite the understanding of convergent morphological specialization in adult sabertooth carnivores, the possibility of a convergent ontogenetic trajectory toward those adult morphologies has not been rigorously examined. The present study examines numerous previously undescribed juvenile nimravid specimens. The results provide insights about nimravid ontogeny and show, for the first time, that the nimravid sabertooth lineage included species in which the permanent upper canine erupted within a lingual concavity of the deciduous upper canine until it reached comparable crown height beyond the alveolar border. Furthermore, this investigation assesses the juvenile morphology and upper canine replacement of felid and barbourofelid sabertooth taxa. The results provide evidence of convergence in deciduous upper canine morphology of three sabertooth carnivore lineages (i.e., nimravid, felid, and barbourofelid), as well as preliminary evidence of convergence in the upper canine replacement process. It might be beneficial for studies of extreme morphological specialization to simultaneously consider convergence in adult morphologies and how morphologies change through ontogeny.