may thus allow hosts to control the identity of their microbial partners, through
secretion of immune effectors and specific bioactive molecules (Douglas 2010;
Hooper et al. 2012; Sommer and Bäckhed 2013).
17.2.3 Morphogenesis and Development
In addition to stimulating the immune system, microbial communities can also
influence the timing and outcomes of transitions in the host’s life. In plants,
microbial communities can influence their host’s phenology by altering flowering,
fruiting, and germination timing and magnitude (Panke-Buisse et al. 2015). Importantly, microbes can mediate the effect of environmental stress on plant phenology
(Yang et al. 2009; Hubbard et al. 2012). In a multigenerational study of drought
responses in Brassica rapa, flower and fruit production were highest when soil
microbes colonizing their roots were preadapted to drought (Lau and Lennon 2012).
Hopefully, these associations can contribute to plant fitness in the face of climate
change.
In animals, these transitions include larval settlement and morphogenesis in rocky
shores, a key step in the life history of diverse intertidal invertebrate taxa. Although it
is clear that larvae respond to surface-bound cues and that receptors are evolutionarily old (Hadfield 2010), the specific mechanisms behind these settling behaviors
remain unknown. Bacteria may be providing larvae with direct benefits such as
increased attachment due to adhesive properties of bacterial exopolysaccharidse
(EPS). Alternatively, bacteria may be releasing signals that represent beneficial
environmental conditions, or reflect conspecific density (Hadfield 2010). Larval
settlement depends on diverse microbial communities for some invertebrate taxa,
while for others, it responds to the presence of specific bacterial taxa. For example,
the marine tubeworm Hydroides elegans can settle on biofilms composed exclusively of Pseudomonas lutoviolaceae (Huang et al. 2012) and scleractininan coral
prefers to settle in shallow waters, where older biofilms (>8 weeks) are dense and
diverse, with high abundances of Gammaproteobacteria (Webster et al. 2004). In
contrast, barnacle settlement is less clear with some studies reporting larval settlement is induced by bacterial biofilms, while in others it is constrained by bacterial
biofilms (Wieczorek et al. 1995; Hadfield 2010). Regardless of the diversity or the
specific mechanism, it is clear that microbial communities can play important roles
in animal development with dramatic consequences for the adult, its reproductive
output, and longevity (McFall-Ngai et al. 2013; Gould et al. 2018; Douglas 2019).
17.2.4 Extended Phenotype
Next generation sequencing techniques renewed interest in the study of the relationships between genotypes and phenotypes of interacting organisms at fine levels,
17 Diversity–Function Relationships and the Underlying Ecological Mechanisms in. . .
303
secretion of immune effectors and specific bioactive molecules (Douglas 2010;
Hooper et al. 2012; Sommer and Bäckhed 2013).
17.2.3 Morphogenesis and Development
In addition to stimulating the immune system, microbial communities can also
influence the timing and outcomes of transitions in the host’s life. In plants,
microbial communities can influence their host’s phenology by altering flowering,
fruiting, and germination timing and magnitude (Panke-Buisse et al. 2015). Importantly, microbes can mediate the effect of environmental stress on plant phenology
(Yang et al. 2009; Hubbard et al. 2012). In a multigenerational study of drought
responses in Brassica rapa, flower and fruit production were highest when soil
microbes colonizing their roots were preadapted to drought (Lau and Lennon 2012).
Hopefully, these associations can contribute to plant fitness in the face of climate
change.
In animals, these transitions include larval settlement and morphogenesis in rocky
shores, a key step in the life history of diverse intertidal invertebrate taxa. Although it
is clear that larvae respond to surface-bound cues and that receptors are evolutionarily old (Hadfield 2010), the specific mechanisms behind these settling behaviors
remain unknown. Bacteria may be providing larvae with direct benefits such as
increased attachment due to adhesive properties of bacterial exopolysaccharidse
(EPS). Alternatively, bacteria may be releasing signals that represent beneficial
environmental conditions, or reflect conspecific density (Hadfield 2010). Larval
settlement depends on diverse microbial communities for some invertebrate taxa,
while for others, it responds to the presence of specific bacterial taxa. For example,
the marine tubeworm Hydroides elegans can settle on biofilms composed exclusively of Pseudomonas lutoviolaceae (Huang et al. 2012) and scleractininan coral
prefers to settle in shallow waters, where older biofilms (>8 weeks) are dense and
diverse, with high abundances of Gammaproteobacteria (Webster et al. 2004). In
contrast, barnacle settlement is less clear with some studies reporting larval settlement is induced by bacterial biofilms, while in others it is constrained by bacterial
biofilms (Wieczorek et al. 1995; Hadfield 2010). Regardless of the diversity or the
specific mechanism, it is clear that microbial communities can play important roles
in animal development with dramatic consequences for the adult, its reproductive
output, and longevity (McFall-Ngai et al. 2013; Gould et al. 2018; Douglas 2019).
17.2.4 Extended Phenotype
Next generation sequencing techniques renewed interest in the study of the relationships between genotypes and phenotypes of interacting organisms at fine levels,
17 Diversity–Function Relationships and the Underlying Ecological Mechanisms in. . .
303