Non-overlap of hosts used by three congeneric and sympatric loranthaceous mistletoe species in an Amazonian savanna: host generalization to extreme specialization

Abstract

Non-overlap of hosts used by three congeneric and sympatric loranthaceous mistletoe species in an Amazonian savanna: host generalization to extreme specialization RESUMO (Não-sobreposição de hospedeiros utilizados por três espécies de ervas-de-passarinho lorantáceas congêneres e simpátricas em uma savana Amazônica: generalização pelo hospedeiro à extrema especialização). Duas hipóteses principais predominam na literatura sobre a especifi cidade entre ervas-de-passarinho e hospedeiros: (1) ervas-de-passarinho só poderão se especializar em espécies de plantas em que elas são frequentemente depositadas; e (2) compatibilidade entre as ervas-depassarinho e as espécies de plantas é um prerequisito para o parasitismo. Explorei estas hipóteses com o estudo dos padrões de deposição de sementes e a compatibilidade entre ervas-de-passarinho e hospedeiros em populações de três espécies de ervas-de-passarinho congenéricas e simpátricas do gênero Psittacanthus (P. biternatus, P. eucalyptifolius and P. plagiophyllus -Loranthaceae) e registrei a presença ou ausência destas três espécies em 15 espécies de árvores em uma mancha de savana na Amazônia. Entre as cinco espécies de árvores que eu encontrei infectadas, também registrei se elas possuíam pelo menos uma semente de erva-de-passarinho de qualquer das espécies aderida aos seus galhos. Finalmente, plantei sementes de todas as espécies de ervas-de-passarinho nas mesmas árvores em várias espécies de hospedeiros e não-hospedeiros e registrei a sobrevivência das sementes e o estabelecimento ao fi nal de 7 (P. plagiophyllus) e 12 meses (P. biternatus e P. eucalyptifolius). Não houve sobreposição entre as árvores utilizadas como hospedeiros pelas três espécies de Psittacanthus. ABSTRACT(Non-overlap of hosts used by three congeneric and sympatric loranthaceous mistletoe species in an Amazonian savanna: host generalization to extreme specialization). Two main hypotheses predominate in the literature on mistletoe-host specifi city: (1) mistletoes are only likely to specialize on plant species on which they are frequently deposited; and (2) compatibility between mistletoes and plant species is a prerequisite for mistletoe-host parasitism. I explored these hypotheses by studying the seed deposition patterns and mistletoe-host compatibility in populations of three congeneric and sympatric mistletoe species of the genus Psittacanthus (P. biternatus, P. eucalyptifolius and P. plagiophyllus -Loranthaceae). I recorded the presence or absence of these mistletoe species in 15 tree species in a savanna patch in Amazonia. Among the fi ve tree species that I found to be potential hosts (at least one tree individual infected), I also recorded if they had at least one mistletoe seed of any species attached to their branches. Finally, I planted seeds of all mistletoe species on the same individual trees in various hosts and non-host species and recorded seed survivorship and seedling establishment within 7 (P. plagiophyllus) to 12 months (P. biternatus and P. eucalyptifolius) aft er planting. Th er...

Host specificity and experimental assessment of the early establishment of the mistletoe Phoradendron crassifolium (Pohl ex DC.) Eichler (Santalaceae) in a fragment of Atlantic Forest in southeast Brazil

“…In the Amazon forest, differences in wood density among tree species have been shown to be unrelated to the likelihood of infection by several Loranthaceae and Viscaceae mistletoes (Pereira 2014). Preferences may also be driven by other host traits, such as bark thickness and xylem resistance, and by the behavior of seed-dispersing frugivorous birds, such as seed treatment (seed manipulation in the bill, bill wiping on twigs and gut passage time) and the frequency of seed deposition, the number of seeds deposited, or a combination of the two (Reid 1989;López de Buen & Ornelas 1999;Arruda et al 2006;Fadini 2011;Guerra & Pizo 2014). In addition, mistletoe survival probability may be affected by potential differences among host plants in terms of the risk of postdispersal seed predation (Fadini et al 2014).…”

“…The seed rain of mistletoes is tied to the post-feeding behavior and plant visiting frequency of their dispersal counterparts (López de Buen & Ornelas 1999;Roxburgh & Nicolson 2005). Some mistletoes are considered generalists and show low host specificity, being able to parasitize several species of host plants, whereas others are considered specialists and infect one or a few common hosts (Norton & Carpenter 1998;Fadini 2011). However, even generalist mistletoes may show preferences for certain hosts (Sargent 1995;Cazetta & Galetti 2007;Arruda et al 2012).…”

Ecology of neotropical mistletoes: an important canopy-dwelling component of Brazilian ecosystems

“…Th e degree of host specifi city can be linked to the scale of observation (Grenfell & Burns 2009). For example, Fadini (2011) showed in a case study that the mistletoe Psittacanthus plagiophyllus Eichl. is extremely specialized to the native cashew tree (Anacardium occidentale L. -Anacardiaceae) in savannas of Alter do Chão, Pará, Brazil.…”

“…Many factors may determine the local degree of host specifi city in mistletoes, e.g., the relative abundance of hosts (Norton & Carpenter 1998), bird perch preferences (Monteiro et al 1992;Cazetta & Galetti 2007), branch architecture (Arruda & Carvalho 2004;Arruda et al 2006), bark thickness (Sargent 1995) and mistletoe-host compatibility (perhaps determined by chemical, physiological and physical processes at the mistletoe-host interface) (Lamont 1983;López de Buen & Ornelas 2002;Fadini 2011). Birds provide the initial fi lter in determining the frequency of seed distribution onto the available hosts, whereas the hosts provide the fi nal fi lter for mistletoe establishment.…”

“…Th ese factors (host relative abundance, bird perch preferences and mistletoehost compatibility) establish the foundation for the development of mistletoe-host interactions. Other characteristics, such as bark rugosity, bark thickness and twig inclination, could play important roles in determining the frequency of distribution of established mistletoes on host trees but they are unlikely to aff ect the range of parasitized hosts (Arruda et al 2006;Fadini 2011). While ecological research has been conducted on the host-mistletoe association from a plant-parasite perspective, other less-studied ecological interactions may also be important.…”