Hummingbird Flower Mites Research Articles

DNA Barcoding Reveals Generalization and Host Overlap in Hummingbird Flower Mites: Implications for the Mating Rendezvous Hypothesis.

AbstractHummingbird flower mites are assumed to monopolize single host plant species owing to sexual selection for unique mating rendezvous sites. We tested the main assumption of the mating rendezvous hypothesis-extreme host specialization-by reconstructing interactions among tropical hummingbird flower mites and their host plants using DNA barcoding and taxonomic identifications. We collected 10,654 mites from 489 flowers. We extracted DNA from 1,928 mite specimens and amplified the cytochrome c oxidase I (CO1) DNA barcode. We analyzed the network structure to assess the degree of generalization or specialization of mites to their host plants. We recorded 18 species of hummingbird flower mites from three genera (Proctolaelaps, Rhinoseius, and Tropicoseius) interacting with 14 species of plants. We found that generalist mites are common, and congeneric mite species often share host plants. Our results challenge the assumption of strict specialization that supports this system as an example of mating rendezvous evolution.

Number of hummingbird visits determines flower mite abundance on hummingbird feeders.

Members of several genera of mites from the family Melicharidae (Mesostigmata) use hummingbirds as transport host to move from flower to flower, where they feed on pollen and nectar. The factors that influence hummingbird flower mite abundance on host plant flowers are not currently known. Here we tested whether hummingbird flower mite abundance on an artificial nectar source is determined by number of hummingbird visits, nectar energy content or species richness of visiting hummingbirds. We conducted experiments employing hummingbird feeders with sucrose solutions of low, medium, and high energy concentrations, placed in a xeric shrubland. In the first experiment, we recorded the number of visiting hummingbirds and the number of visiting hummingbird species, as well as the abundance of hummingbird flower mites on each feeder. Feeders with the highest sucrose concentration had the most hummingbird visits and the highest flower mite abundances; however, there was no significant effect of hummingbird species richness on mite abundance. In the second experiment, we recorded flower mite abundance on feeders after we standardized the number of hummingbird visits to them. Abundance of flower mites did not differ significantly between feeders when we controlled for hummingbird visits. Our results suggest that nectar energy concentration determines hummingbird visits, which in turn determines flower mite abundance in our feeders. Our results do not support the hypothesis that mites descend from hummingbird nostrils more on richer nectar sources; however, it does not preclude the possibility that flower mites select for nectar concentration at other spatial and temporal scales.

Effects of Pollen in Lobelia laxiflora (Lobeliaceae) Long-Lived Flowers on Fecundity of Tropicoseius chiriquensis (Acari: Mesostigmata: Ascidae)

Abstract Pollen and nectar are the most important floral rewards in plant—pollinator interactions. These rewards are voraciously consumed by hummingbird flower mites (Acari: Mesostigmata: Ascidae), and nectar and pollen feeding by mites have a strong impact on plant—hummingbird interactions. Tropicoseius chiriquensis (Acari: Mesostigmata: Ascidae) feed on nectar and pollen of Lobelia laxiflora H.B.K. (Lobeliaceae) flowers, and within the floral corolla they mate and lay eggs. Yet the benefits of nectar and pollen feeding in terms of survival and fecundity of flower mites are quite unexplored. Here, we evaluate the fecundity and numerical response of T. chiriquensis to the availability of pollen in long-lived protandrous flowers of L. laxiflora. Under field conditions, unmanipulated flowers with pollen had more mites (adults, nymphs, larvae, and eggs) than emasculated flowers without pollen, Numbers of mites fluctuated throughout the flower life span. More adult mites were found for the first 2 d of the flower (staminate phase) and decreased for the last three days of life of the flower (pistillate phase). In contrast, we found higher number of larvae in the pistillate phase. In a laboratory experiment, the fecundity of flower mites was 4 times as high when pollen was available as that when flower mites were not provided with pollen. They completed their life cycle in approximately a week, the life span of L. laxiflora flowers. Our results suggest that pollen availability in L. laxiflora long-lived flowers could influence the population dynamics of T. chiriquensis by having a positive impact on numbers and fecundity of the mites.

The Effect of Hummingbird Flower Mites on Nectar Availability of Two Sympatric Heliconia Species in a Brazilian Atlantic Forest

Hummingbird flower mites feed and reproduce in flowers of host plants pollinated by hummingbirds, and use the nostrils and bill of the hummingbird to move from plant to plant. These mites compete with the pollinator for the nectar produced by flowers. An investigation was made of the relationship between the pattern of nectar production and the effects of hummingbird flower mites in the flowers of two sympatric species of Heliconia (Heliconiaceae). Nectar production was sampled by carrying out two experiments: 2-hour intervals and accumulated nectar. Flowers with and without mites were used in both experiments. Exclusion of mites increased nectar production, especially in accumulated daily production (a maximum of 49 % more nectar). Both Heliconia species had the same pattern of nectar production: a high concentration in the morning, which was progressively reduced as the day passed. This pattern of nectar production coincides with the behaviour of the pollinator, which makes more frequent visits in the morning, as observed in a previous study. The results suggest that the impact of mites on nectar availability of Heliconia is more important with regard to total volume of nectar produced irrespective of flower longevity. A high variation among individuals in nectar produced in the populations was also observed. Hummingbird flower mites strongly affect availability of nectar for hummingbirds.

Ascid mites (Acari: Mesostigmata: Ascidae) from Costa Rican hummingbirds (Aves: Trochilidae), with description of three new species and a key to the Proctolaelaps belemensis species group

Eleven species of hummingbird flower mites of the genera Proctolaelaps Berlese, 1923, Tropicoseius Baker & Yunker, 1964 and Rhinoseius Baker & Yunker, 1964 were recorded from hummingbirds in Costa Rica. Three new species of the genus Proctolaelaps are described and figured, i.e. P. threnetes Dusbabek & Literak, sp. nov., P. naskreckii Dusbabek & Havlicek, sp. nov. and P. chalybura Dusbabek & Capek, sp. nov. A key for identification of females and males of the P. belemensis species group is included. Five species of the genus Tropicoseius and three species of the genus Rhinoseius are recorded, three of these species are recorded from Costa Rica for the first time.

Flower mites and nectar production in six hummingbird-pollinated plants with contrasting flower longevities

Hummingbird flower mites and hummingbirds may compete intensely for the nectar secreted by their host plants. Here, we present the results from field experiments in which flower mites were excluded from flowers of six hummingbird-pollinated plants with contrasting flower longevities. Nectar measurements were taken on flowers from which mites were excluded and those without mite exclusion over their lifespans. The exclusion of mites had a significant positive effect on the amount of nectar available in plants with long-lived flowers. In contrast, nectar availability in short-lived flowers was not significantly reduced after mite exclusion. The significance of the mite-exclusion treatment was independent of floral morph and flower age. Results also suggest that the magnitude of the mite-exclusion treatment depends on the volume of nectar produced by the flower throughout its lifetime. The treatment effect was detected when nectar consumption, presumably by flower mites, exceeded 13% of the nectar produced by the flowers; nectar availability was not significantly reduced when nectar volume was < 7 µL per flower. It appears that flower mites consume proportionately more nectar in long-lived flowers than in short-lived flowers. Parasitic hummingbird flower mites seem to be preferentially taking advantage of plant-pollinator interactions in which flowers last several days and produce large volumes of nectar. The consequences of this finding concerning plant–hummingbird–mite interactions await further investigation. As a working hypothesis, we propose that nectar production has increased over evolutionary time not only by the selective pressures imposed by the pollinators, but also to compensate for the reduction they suffer after exploitation by nectar robbers and thieves such as flower mites.Key words: Ascidae, flower longevity, hummingbird pollination, multiple-species interactions, mutualism exploitation, nectar theft.

Effects of nectar theft by flower mites on hummingbird behavior and the reproductive success of their host plant,Moussonia deppeana(Gesneriaceae)

Hummingbird flower mites are transported in the nares of hummingbirds and may compete with them by “robbing” nectar secreted by the host plants. We have shown thatTropicoseiussp. flower mites consume almost half the nectar secreted by the long‐lived, protandrous flowers ofMoussonia deppeana(Gesneriaceae) pollinated byLampornis amethystinus(Trochilidae). In this paper, we ask whether mimicking nectar consumption of flower mites alters some aspects of hummingbird foraging patterns, and, if so, how this affects host plant seed production. We observed hummingbirds foraging on (a) plants in which nectar was removed from the flowers and then filled with a sugar solution to half the volume of nectar simulating nectar consumption by flower mites, and (b) plants where nectar was removed and then filled with the sugar solution up to normal nectar volumes. Flower mites were excluded from both groups of plants to control for mite activity. Hummingbirds made fewer but longer visits to plants and revisited more the flowers with nectar removal than those without the treatment. We then conducted a pollination experiment on pistillate flowers using a stuffedL. amethystinushummingbird to evaluate the effect of pollination intensity (number of bill insertions into one flower) on seed production. Flowers with more insertions produced significantly more seeds than those flowers that received fewer insertions. We conclude that the simulation of nectar consumption by hummingbird flower mites can influence the behavior of the pollinator, and this may positively affect seed production.

Nectar ‘theft’ by hummingbird flower mites and its consequences for seed set in Moussonia deppeana

Summary Mites (Acari: Mesostigmata: Ascidae) that live and feed in the flowers of about 100 plant species are transported in the nares of hummingbirds (Trochilidae). Mites may compete with hummingbirds for nectar secreted by the host plants, and this could affect the dynamics and reproductive outcomes of the mutualism between plants and their pollinating hummingbirds. Here we combined field observations and experimental manipulations to assess the role of hummingbird flower mites (Tropicoseius sp. nov.) on nectar secretion and reproductive output of protandrous Moussonia deppeana (Schlecht. & Cham.) Hanst. (Gesneriaceae) during their flowering period in a cloud forest remnant. During the 4 days that the flowers of M. deppeana last, flowers were visited exclusively by hummingbirds (Lampornis amethystinus). Bud production per inflorescence peaked in December. There were few open flowers per inflorescence in November, but numbers increased as the flowering season progressed (December and January). The availability of each flower phase differed over the flowering season. Staminate‐phase flowers were more abundant over the flowering season than pistillate‐phase flowers. These differences were statistically significant over time. Nectar availability was reduced by up to 50% in the presence of hummingbird flower mites. Over the 4 days of observation, significantly more nectar was secreted to flowers from which mites were excluded than to flowers with no mite exclusion. The same effect was observed during flowering, but mites consumed a greater percentage of the total nectar secreted in December. Significantly more nectar was secreted during the staminate phase than in the pistillate phase, independent of time and treatment. A manual pollination experiment suggested that mites act like secondary pollinators in this self‐compatible, non‐autogamous plant, at least in flowers that were not pollinated manually and had no access to pollinating hummingbirds. Although seed production was not reduced significantly by flower mites, our results suggest that the presence of floral mites can affect pollen transmission, as the amount of nectar available to hummingbirds was reduced drastically. This can directly affect hummingbird foraging patterns and reduce the fitness of the host plants.

Sexual Sorting in Hummingbird Flower Mites (Mesostigmata: Ascidae)

Hummingbird flower mites (Rhinoseius Baker & Yunker and Tropicoseius Baker & Yunker, and certain Proctolaelaps Berlese species; Acari: Mesostigmata: Ascidae) feed on nectar and pollen, mate, and oviposit in the inflorescences of hummingbird pollinated plants and are phoretic in the nasal cavities of hummingbirds. Unlike many phoretic mites, males as well as females of most of these species disperse on the phoretic host (hummingbirds). Theory suggests that male dispersal may increase mating success in species in which breeding groups are small and males can seek groups with a more favorable (more female-biased) sex ratio by dispersing, a process we call sexual sorting. Laboratory experiments in which mites were confined to a lattice of interconnected capillary tubes, some with nectar present to simulate flowers, showed that both Proctolaelaps kirmsei Fain Hyland, & Aitken and Proctolaelaps sp. nov. #1 from La Selva, Costa Rica, demonstrate significant sexual sorting. Field census data from the same site for P. kirmsei showed that, consistent with theory and the laboratory results, sexual sorting also occurs in nature among incipient mite breeding groups on inflorescences, when these groups are small.

Importance of pollen and nectar in flower choice by hummingbird flower mites, Proctolaelaps kirmsei (Mesostigmata: Ascidae)

Proctolaelaps kirmsei (Mesostigmata: Ascidae) is a specialist flower mite that feeds on pollen and nectar in flowers of Hamelia patens (Rubiaceae). We offered mites a choice between pairs of manipulated H. patens flowers in petri dishes in the laboratory, then counted the number of mites inside the flowers after 1 hour. Relative to flowers with stamens and nectaries removed, there were more mites in flowers with only stamens, with only nectaries, and with both stamens and nectaries. When offered a choice between flowers with stamens but no nectaries versus flowers with nectaries but no stamens, the mites did not show a preference. Mites preferred H. patens flowers with H. patens stamens over those with the stamens of a coexisting non-host plant (Heliconia pogonantha; Heliconiaceae) inserted, so the identity of the pollen is important in flower choice. These results and previous work on the importance of nectar show that the presence of both pollen and nectar can be used by P. kirmsei to discriminate between flowers. Some caution is required in extrapolating from laboratory choice tests to behavior of the mites in the field.

Effects of Nectar Consumption by the Hummingbird Flower Mite Proctolaelaps kirmsei on Nectar Availability in Hamelia patens

Hummingbird flower mites consume nectar and pollen in the flowers they inhabit and are transported on hummingbirds. This study, conducted at La Selva Biological Station in Costa Rica, measured the effects of the mite Proctolaelaps kirmsei (Gamasina: Ascidae) and of pollinating hummingbirds on nectar volume of Hamelia patens (Rubiaceae), by replicated exdusion experiments. The mites consume, on average, some 40 percent of the nectar produced by flowers, when hummingbirds are exduded. Mites and hummingbirds together consume about 85 percent of the nectar. Individual trees in the study differed significandy and independently in both nectar production and mite population density. These results help establish hummingbird flower mites as significant plant parasitesespecially considering their concomitant role as voracious consumers of pollen (Paciorek et al. 1995)-as well as important competitors with hummingbirds for the nectar of their host plants. Published estimates of nectar production rates in mite host plants may be seriously in error, unless mites were exduded.

Making Sense of Ecological Complexity: A Personal and Conceptual Restrospective

The Organization for Tropical Studies (OTS/OET) played an important role in the development of population and community biology during the first 25 years of the organization's existence. The author traces changes in the conceptual framework of community ecology during this period, using examples from his own work with hummingbird flower mites and from the tropical research of others who have been associated with OTS. The principal lesson to be learned from this period is that the same pattern may result from several different processes; there are distinct, valid explanations for different cases of what tropical ecologists used to see as a unitary phenomena.

Heterogeneity of Tropical Floral Microclimates and the Response of Hummingbird Flower Mites

Analyses of microclimatic patterns on Heliconia wagneriana inflorescences inhabited by nectarivorous hummingbird flower mites (Gamasida: Ascidae) in secondary lower montane rainforest reveal the existence of substantial microclimatic variation both among and within individual inflorescences. Field experiments demonstrate that the mites respond to this variation by exploiting thermally favorable locations and avoiding thermally adverse conditions within inflorescences. Field introductions of mite population inocula to uninhabited inflorescences show that mite reproduction (and probably survival) is affected strongly by inflorescence microclimate. Floral microclimate, in conjunction with hummingbird visitation patterns, controls mite dispersal among inflorencences. These experiments illustrate the impact of microclimatological heterogeneity on the population biology of a tropical phytophagous arthropod.

Flowering patterns of long-lived Heliconia inflorescences: implications for visiting and resident nectarivores.

Flowering patterns of four Heliconia (Heliconiaceae) species in Trinidad, West Indies were examined for their predictability and availability to the nectarivores that rely on Heliconia floral nectar. Principal flower visitors are trapling hermit hummingbirds; inflorescences are inhabited by nectarivorous hummingbird flower mites that move between inflorescences by riding in the hummingbirds' nares. Heliconia inflorescences flower for 40-200 days, providing long-term sources of copious nectar (30-60 μl per flower), but each Heliconia flower lasts only a single day. As an inflorescence ages the interval increases between open flowers within a bract; wet-season inflorescences produce open flowers more slowly than dry-season conspecifics.Estimated daily energy expenditures for hermit hummingbirds demonstrate that slow production of short-lived open flowers plus low inflorescence density preclude territorial defense of Heliconia by the hermits. Heliconia flowering patterns are viewed as a means of (i) regulating reproductive investment by the plants through staggered flower production over long periods of time, and (ii) maintaining outcrossing by necessitating a traplining visitation pattern by its hummingbird pollinators. I suggest that Heliconia exhibit a two-tiered pollination system by using hermit hummingbirds primarily for outcrossing and using hummingbird flower mites primarily for self-pollination.