Yumi Oki

Relationships between endophyte diversity and leaf optical properties

A single tropical plant species can harbour hundreds of endophyte species within its tissues. Beyond this, little is known about the relationship between endophyte colonization, leaf traits and spectral properties of leaves. We explore these relationships in Coccoloba cereifera, a plant well known for its symbiotic properties. Endophyte richness in C. cereifera was statistically correlated with leaf traits such as water content, the ratio of fresh weight/dry weight and polyphenol/leaf specific weight. Endophyte diversity was also related to spectral vegetation indices of chlorophyll content. The associations among endophyte diversity, leaf traits and spectral reflectance pose new questions and present new opportunities to better understand plant–fungal symbioses and related leaf optical properties.

Hail impact on leaves and endophytes of the endemic threatened Coccoloba cereifera (Polygonaceae)

There is increasing evidence that some natural disturbances are increasing in frequency and intensity with global change, but the effects of these changes on plant populations is poorly understood. It is estimated that for every 1°C increase in the summer mean minimum temperature, there is a 40% increase in hail damage. Severe hailstorms can cause large impacts on biological communities. In 2008, a strong hailstorm hit the speciose and endemic rupestrian vegetation in Serra do Cipó, Brazil. This event prompted us to record its effects on the narrowly distributed and threatened species Coccoloba cereifera (Polygonaceae). About 33 to 60% of the leaves on the 246 individuals surveyed were lost. The disturbance also influenced some of the physiological traits of C. cereifera, increasing the concentration of photosynthetic pigments (chlorophyll and carotenoid) and polyphenols in the leaves. The most pronounced increase of chlorophyll was in young leaves (ca. 60%). Carotenoid content increased by ca. 50% in all leaf ages, while polyphenols increased tenfold. Contrarily, the endophyte richness decreased drastically after the event (from 104 to 33 species), only 12% of similar species remain. The hail storm strongly influenced all variables evaluated in this study, i.e., structure, physiology, and associated fungi. These results show that hailstorm had a dramatic and immediate impact on C. cereifera and may also severely affect other endemic or threatened plant species. Therefore, it is imperative that we broaden our knowledge on global climate change impacts for the conservation of native species.

Distribution of the endophytic fungi community in leaves of Bauhinia brevipes (Fabaceae)

Endophytic fungi represent large, yet unexplored components of biodiversity. This work evaluated the richness and the distribution of endophytes in the leaves of Bauhinia brevipes (Fabaceae). A total of 1110 colonies were recovered from the samples and grouped by their morphological traits into 126 taxa. The total number of taxa according to leaf development was: 102 in mature leaves, 93 in recently expanded leaves and 79 for unfolded leaves. The major endophyte genera were Phomopsis, followed by Dothiorella, Pestalotiopsis and Acremonium. The richness and the isolate numbers of endophytes were not statistically affected by leaf region. However, some taxa were leaf-age specific; six were isolated only from unfolded leaves, nine from recently expanded leaves and 17 were exclusively found in mature leaves. The composition of endophytes varied with leaf region; the similarities (Jaccards Index) among the leaf regions of different leaf ages ranged from 0.36 to 0.46, indicating a high spatial variation in the community of endophytic fungi inside the leaves. The high richness of endophytes in this host plant highlights a significant contribution of fungi to tropical biodiversity and the need for further research in this area.

Baccharis: A Neotropical Model System to Study Insect Plant Interactions

The genus Baccharis is composed of ca. 500 species which are distributed primarily in tropical America. It is dioecious and highly diverse in chemistry, architecture, phenology and occupy many different niches across several gradients of light, temperature, humidity, altitude and succession. It is host to the most speciose galling fauna, with more than 121 galling species on 40 host plant. This system provides an ideal scenario to test several ecological hypotheses, including the long standing plant sexual differences on timing and intensity of energy allocation, vigor, architecture and herbivore attack. Moreover its wide distribution enables to test latitudinal and altitudinal gradients on gall attack. We review the studies performed on these Neotropical shrubs related to galling insects. These studies have been crucial for the establishment of generalities and testing of ecological and evolutionary theories across the Americas, as well as to generate new ideas and hypotheses. For these reasons and power of the field and experimental observations we suggest that the galling insects on their Baccharis hosts may represent a Neotropical model system for studies on insect plant interactions.

Multitrophic interactions among fungal endophytes, bees, and Baccharis dracunculifolia: resin tapering for propolis production leads to endophyte infection

The tropics are known for their high diversity of plants, animals, and biotic interactions, but the role of the speciose endophytic fungi in these interactions has been mostly neglected. We report a unique interaction among plant sex, bees, and endophytes on the dioecious shrub, Baccharis dracunculifolia (Asteraceae). We assessed whether there was an association between resin collection by bees and fungal endophytes considering the host plant sex. We hypothesized that resin collection by the Africanized honey bee, Apis mellifera L. (Apidae) could favor the entry of endophytes in B. dracunculifolia. Specifically, we tested the hypotheses that (1) bees damage the leaf buds of female and male plant at different proportions; (2) damage on leaf buds increases the richness of endophytic fungi; (3) endophyte richness differs between female and male plants; and (4) in vitro growth of endophytes depends on the sex of the plant individual from which the resin was extracted. Endophyte richness and proportion of leaf bud damage did not vary between the plant sexes. However, species similarity of endophytes between female and male plants was 0.33. Undamaged leaf buds did not show culturable endophytes, with all fungi exclusively found in damaged leaf buds. Endophyte composition changed with the plant sex. The endophytes exclusively found in female plants did not develop in the presence of male resin extract. These findings highlight that resin collection by A. mellifera for propolis production favors the entry of endophytic fungi in B. dracunculifolia. Additionally, endophyte composition and growth are influenced by plant sex.

The influence of the endophytic fungi on the herbivores from Baccharis dracunculifolia (Asteraceae)

Endophytic fungi have an important role in the mediation of the plant-herbivores, plantpathogens and plant-environment interaction. To understand the interaction between endophytic fungi and Baccharis dracunculifolia (Asteraceae) and these with the herbivores, the following hypotheses were investigated: (i) the number of endophytic morphospecies (richness) increases with leaf age; (ii) the richness of endophytes varies with seasonality; (iii) the richness of endophytes varies with the plant gender; (iv) there is negative correlation between the richness of endophytes and richness of herbivores; and (v) there is negative correlation between the richness of endophytes and abundance of herbivores. Monthly, the leaves of B. dracunculifolia were collected in Estacao Ecologica da UFMG from October, 2006 to August, 2007. In total, we found eight endophytic morphospecies, a low number when compared to the results found in other study in the same plant species. Mature leaves had higher richness, mainly during the wet season. In relation to gender, the richness was equal. It was also observed that the richness of endophytes found in leaves did not influence the richness and abundance of herbivores. All the results of this work indicated that the environment has fundamental role in the determination of the endophytic community and in the Baccharis -herbivores interaction. Key words: Baccharis , Cerrado, endophytic fungi, herbivores, Asteraceae.

Arbuscular Mycorrhiza and Endophytic Fungi in Ruspestrian Grasslands

Rupestrian grasslands are a biodiversity hotspot for arbuscular mycorrhizal fungi (AMF) and endophytic fungi. These groups have major influence on the structure and dynamics of the plant community in this ecosystem. AMF are generalists, associating with a wide variety of host plants , while endophytic fungi tend to establish more specific relations with host plants. AMF distribution is mainly influenced by soil attributes, while the distribution of endophytic fungi is mostly driven by the host plant. Both fungal groups influence the host plant metabolism and ecology , enhancing the host plant survival in this harsh ecosystem. There are no studies relating both fungal groups in rupestrian grasslands. A strong relation may exist between them, and exploring this gap will contribute to the understanding of this unique ecosystem and the relations in it.