Community assembly, functional traits, and phylogeny in Himalayan river birds

“We used the R packages “ape” and “phytools” (Paradis et al., 2004; Revell, 2012) to obtain a consensus tree for our 15 target species using a pseudo- posterior distribution (https://birdt ree.org/subse ts/) from 1000 random samples from the “backbone tree” after applying the 50% majority rule…”

“We used the R packages “ape” and “phytools” (Paradis et al., 2004; Revell, 2012) to obtain a consensus tree for our 15 target species using a pseudo- posterior distribution (https://birdt ree.org/subse ts/) from 1000 random samples from the “backbone tree” after applying the 50% majority rule…”

“Growing concern about the global status of freshwater ecosystems is also prompting interest in interactions between natural biodiversity patterns in rivers and the effects of environmental change (see Dudgeon et al., 2006).”

“…(SR) offered a simple measure of taxonomic diversity at each site, phylogenetic diversity (PD) was calculated as Faith's PD index, or the sum of all branch lengths of the phylogeny connecting all species at a site (Faith, 1992), using the function “pd” in R package picante (Kembel et al., 2010).”

“…across river reaches surveyed as 15 species abundances*68 sites), R (environmental characteristics of samples: 68 sites*12 environmental variables), and Q (species traits: 15 species*8 traits) were analyzed separately using different ordination methods in “ade4” package in R (Dray & Dufour, 2007).”

“…(SR) offered a simple measure of taxonomic diversity at each site, phylogenetic diversity (PD) was calculated as Faith's PD index, or the sum of all branch lengths of the phylogeny connecting all species at a site (Faith, 1992), using the function “pd” in R package picante (Kembel et al., 2010).”

“Observed versus expected contrast variances were compared under a null model created by swapping the tips of the phylogenetic tree to test for significance differences (Blomberg et al., 2003).”

“Given that ecosystem character changes in time and space, conditions under which species assemble and co- exist must also vary (McGill et al., 2006).”

“…evolutionary forces, environmental conditions, and interspecies interactions combine to structure local communities (Cavender- Bares et al., 2009; Webb et al., 2002), with prominent theories proposing either neutral or deterministic processes (Chase & Myers, 2011; Kembel, 2009; Swenson &…”

“As a basis for all subsequent phylogenetic analysis, we prepared a phylogenetic tree for the species in our community by trimming from the original phylogeny available from www.birdt ree.org (Jetz et al., 2012; Figure S2).”

“Absolute functional diversity was estimated as functional richness, FRic (Villéger et al., 2008), which represents the multidimensional volume of functional space occupied by the species within a community (Villéger et al., 2008).”

“In this study, we use specialist river birds to examine Southwood's original premise (Southwood, 1977; Southwood, 1988), restated for rivers by Townsend and Hildrew (1994), that habitats provide the templet through which evolutionary forces act with phylogeny to determine species' life history.”

“Among all ecosystems, rivers have received considerable emphasis in community ecology (Altermatt et al., 2020; Robinson et al., 2002; Ward et al., 1998), including seminal assessments of assembly rules, environmental filtering, and trait- based studies (Heino et al., 2015; Poff, 1997).”

“These effects arise because river catchment ecosystems are both hotspots for biological diversity and hotspots for resource exploitation (Strayer & Dudgeon, 2010).”

“…forces, environmental conditions, and interspecies interactions combine to structure local communities (Cavender- Bares et al., 2009; Webb et al., 2002), with prominent theories proposing either neutral or deterministic processes (Chase & Myers, 2011; Kembel, 2009; Swenson & Enquist, 2009).”

“An important proviso in studying species and trait assembly in communities is that species relatedness should be controlled or represented in order to eliminate phylogeny as a potential confound (Cadotte & Tucker, 2017; Kraft et al., 2015; Mayfield & Levine, 2010).”

“…connectivity, and impair water quality, and across the world, these processes are contributing to the decline or elimination of specialist organisms and population reductions that are among the fastest of any global ecosystem (Bower & Winemiller, 2019; Evans et al., 2018; Tickner et al., 2020).”

“In this study, we use specialist river birds to examine Southwood's original premise (Southwood, 1977; Southwood, 1988), restated for rivers by Townsend and Hildrew (1994), that habitats provide the templet through which evolutionary forces act with phylogeny to determine species' life history.”

“Understanding how species assemble into communities is one of the most fundamental themes in ecology (Gerhold et al., 2015; Götzenberger et al., 2012; Weiher et al., 2011).”

“In this study, we use specialist river birds to examine Southwood's original premise (Southwood, 1977; Southwood, 1988), restated for rivers by Townsend and Hildrew (1994), that habitats provide the templet through which evolutionary forces act with phylogeny to determine species' life history.”

“Traits also reflect species' roles or functions within communities and can reveal mechanisms that affect distributional patterns along habitat gradients (Kraft et al., 2007).”

“Trait and community responses to environmental gradients were ordinated using an RLQ framework, a multivariate technique that summarizes joint structure among matrices (Dray et al., 2014; Dray & Legendre, 2008).”

“…similarity— is expected to exclude similar species from co- existing (Macarthur & Levin, 1967), environmental filtering and niche shifts act to moderate the extent to which similar species co- occur in similar habitat conditions (Gerhold et al., 2015; Ulrich et al., 2018; Weiher et al., 2011).”

“Trait and community responses to environmental gradients were ordinated using an RLQ framework, a multivariate technique that summarizes joint structure among matrices (Dray et al., 2014; Dray & Legendre, 2008).”

“…ecosystems, for example, competition, trait expression, and environmental filtering along elevational gradients can have marked effects on bird communities (Chiu et al., 2020; Dehling et al., 2014; Ding et al., 2019; He et al., 2018; Machac et al., 2011; McCain, 2009; Ulrich et al., 2018).”

“…similarity— is expected to exclude similar species from co- existing (Macarthur & Levin, 1967), environmental filtering and niche shifts act to moderate the extent to which similar species co- occur in similar habitat conditions (Gerhold et al., 2015; Ulrich et al., 2018; Weiher et al., 2011).”

“We also used Moran's correlograms, plotted using the function “phyloCorrelogram” from the package “phylosignal” (Keck et al., 2016), to assess how phylogenetic autocorrelation changed across different phylogenetic distances.”

“Notwithstanding these caveats, our study revealed clear relationships among river character, species traits, and community composition of river birds in the Himalayan Mountains aided by the increasingly used RLQ analysis (Ribera et al., 2001).”

“The rationale behind this was that environmental filtering would lead to a decrease in trait range or variance in communities (e.g., Graham et al., 2009; Zhang et al., 2020).”

“…forces, environmental conditions, and interspecies interactions combine to structure local communities (Cavender- Bares et al., 2009; Webb et al., 2002), with prominent theories proposing either neutral or deterministic processes (Chase & Myers, 2011; Kembel, 2009; Swenson & Enquist, 2009).”

“…forces, environmental conditions, and interspecies interactions combine to structure local communities (Cavender- Bares et al., 2009; Webb et al., 2002), with prominent theories proposing either neutral or deterministic processes (Chase & Myers, 2011; Kembel, 2009; Swenson & Enquist, 2009).”

“Ideally, investigations aimed at understanding communities should blend field observations with some assessment of the functional and phylogenetic identities of the component species (McGill et al., 2006; Winemiller et al., 2015; Xu et al., 2017).”

“The L- species table was analyzed using correspondence analysis (CA), while the R- environmental variables table and Q- trait table were analyzed by a Hill– Smith PCA combining quantitative and qualitative variables using CA species scores as a column weight to couple Q and L (Brown et al., 2014).”

“…effort into community assembly has focused on high- energy river systems in mountain landscapes, where large altitudinal ranges, complex topography, and geomorphological dynamism give rise to pronounced ecological gradients with large species turnover (Jacobsen et al., 1997; Ormerod et al., 1994).”

“…foraging or by exploiting the subsidy of food resources that reaches the riparian zone by export from the river channel (Buckton & Ormerod, 2008; Petersen et al., 2004); (ii) they occupy habitats created specifically by the fluvial geomorphological system linked to high energy rivers for most…”

“Among all ecosystems, rivers have received considerable emphasis in community ecology (Altermatt et al., 2020; Robinson et al., 2002; Ward et al., 1998), including seminal assessments of assembly rules, environmental filtering, and trait- based studies (Heino et al., 2015; Poff, 1997).”

“…a land disturbance gradient (Ribera et al., 2001), plants along a salinity gradient (Pavoine et al., 2011), ants along a complexity gradient (Weischer et al., 2012), bats across a gradient of forest fragmentation (Farneda et al., 2015), and birds with urbanization (Evans et al., 2018).”

“These patterns are consistent with the hypothesis that altitudinal trends affect these communities through environmental filtering (Dehling et al., 2014; Hanz et al., 2019; Vollstädt et al., 2017).”

“…effort into community assembly has focused on high- energy river systems in mountain landscapes, where large altitudinal ranges, complex topography, and geomorphological dynamism give rise to pronounced ecological gradients with large species turnover (Jacobsen et al., 1997; Ormerod et al., 1994).”

“…relevant traits are conserved or modified along any given phylogeny, thereby providing evidence about the roles of environmental filtering and competitive segregation in assembly processes (Cavender- Bares et al., 2009; Pavoine et al., 2008; He et al., 2018; reviewed in Cadotte et al., 2019).”

“…relevant traits are conserved or modified along any given phylogeny, thereby providing evidence about the roles of environmental filtering and competitive segregation in assembly processes (Cavender- Bares et al., 2009; Pavoine et al., 2008; He et al., 2018; reviewed in Cadotte et al., 2019).”

“Bird species that depend on aquatic production and occupy the riparian zone of Himalayan rivers were known from reconnaissance surveys and previous studies (Buckton & Ormerod, 2002; Manel et al., 2000).”

“The branch lengths are taken to represent evolutionary time, with higher PD indicating group of species that are more evolutionarily apart in time (Tucker et al., 2019).”

“Among all ecosystems, rivers have received considerable emphasis in community ecology (Altermatt et al., 2020; Robinson et al., 2002; Ward et al., 1998), including seminal assessments of assembly rules, environmental filtering, and trait- based studies (Heino et al., 2015; Poff, 1997).”

“Among all ecosystems, rivers have received considerable emphasis in community ecology (Altermatt et al., 2020; Robinson et al., 2002; Ward et al., 1998), including seminal assessments of assembly rules, environmental filtering, and trait- based studies (Heino et al., 2015; Poff, 1997).”

“…connectivity, and impair water quality, and across the world, these processes are contributing to the decline or elimination of specialist organisms and population reductions that are among the fastest of any global ecosystem (Bower & Winemiller, 2019; Evans et al., 2018; Tickner et al., 2020).”

“Ideally, investigations aimed at understanding communities should blend field observations with some assessment of the functional and phylogenetic identities of the component species (McGill et al., 2006; Winemiller et al., 2015; Xu et al., 2017).”

“The table gives Blomberg’s K values with significance values (in parentheses) handling (Ormerod & Tyler, 1991).”

“First, at a global level, the association between overall bird richness and habitat heterogeneity is a well- known phenomenon, especially for species that are specialized for particular habitat types— in this case, high- energy rivers (Larsen et al., 2010; Robinson et al., 2002).”

“These patterns are consistent with the hypothesis that altitudinal trends affect these communities through environmental filtering (Dehling et al., 2014; Hanz et al., 2019; Vollstädt et al., 2017).”

“Bird species that depend on aquatic production and occupy the riparian zone of Himalayan rivers were known from reconnaissance surveys and previous studies (Buckton & Ormerod, 2002; Manel et al., 2000).”

“…ecosystems, for example, competition, trait expression, and environmental filtering along elevational gradients can have marked effects on bird communities (Chiu et al., 2020; Dehling et al., 2014; Ding et al., 2019; He et al., 2018; Machac et al., 2011; McCain, 2009; Ulrich et al., 2018).”

“We suggest that community assembly in high- altitude river birds must therefore reflect a blend of phylogenetic constraint and habitat filtering coupled with some proximate niche- based selection of trait character for specialization (Morelli et al., 2019; Reif et al., 2016).”

“…connectivity, and impair water quality, and across the world, these processes are contributing to the decline or elimination of specialist organisms and population reductions that are among the fastest of any global ecosystem (Bower & Winemiller, 2019; Evans et al., 2018; Tickner et al., 2020).”

“Furthermore, functional approaches fail to account for within- species variations across populations while the phylogenetic approach can inflate signals related to certain traits (Zhao et al., 2020).”

“In part, this interest reflects the pronounced environmental gradients represented by rivers both longitudinally and among contrasting river basins that together have created a diverse habitat template into which species have proliferated (Terui et al., 2021; Townsend & Hildrew, 1994).”

“…ecosystems, for example, competition, trait expression, and environmental filtering along elevational gradients can have marked effects on bird communities (Chiu et al., 2020; Dehling et al., 2014; Ding et al., 2019; He et al., 2018; Machac et al., 2011; McCain, 2009; Ulrich et al., 2018).”

“Moreover, despite being conspicuous components of the global riverine fauna, river birds have been neglected in fundamental studies of mechanisms structuring communities, especially in mountainous areas (Manel et al., 2000; Sinha et al., 2019).”

“…relevant traits are conserved or modified along any given phylogeny, thereby providing evidence about the roles of environmental filtering and competitive segregation in assembly processes (Cavender- Bares et al., 2009; Pavoine et al., 2008; He et al., 2018; reviewed in Cadotte et al., 2019).”

“…either by direct aquatic foraging or by exploiting the subsidy of food resources that reaches the riparian zone by export from the river channel (Buckton & Ormerod, 2008; Petersen et al., 2004); (ii) they occupy habitats created specifically by the fluvial geomorphological system linked to high…”

“In a similar vein, measurements of the availability or abundance of prey used by any of the species were beyond the capabilities of this study, even though prey abundance is known to influence the density of river birds (Ormerod, 1985; Ormerod & Tyler, 1991).”

“Some species in our study were associated with the least modified river reaches where bank vegetation, geomorphological structure, and flow patterns were unimpaired and expected to support abundant prey (Ormerod & Tyler, 1987, 1991; Sinha et al., 2019).”

“…or functional tree “T” with a set of species “n” represented by a subset of branching nodes, the MPD of “n” is MPD(orMFD) = ∑n i ∑n j i,j n (i ≠ j) equal to the average of the distances of all possible simple paths in “T” that connect pairs of nodes in “n” (Tsirogiannis & Sandel, 2014).”

“This visit frequency is considered appropriate for detecting specialist river birds that occupy linear territories (D'Amico & Hemery, 2003).”

“Areas above 1500 m in the northwest Himalaya are highly seasonal with cold winters and mild summers (Barve, 2017).”

“In the breeding season (Figure 3a), traits such as beak length, tail length, and tarsus length have a strong explanatory power on avian distribution (importance > 99%), consistent with the functional trait environmental filtering theory [57,58].”

“These are recognized pressures on river ecosystems known to affect river bird distribution in the Himalaya (Vaughan et al. 2007; Sinha et al. 2019, 2022).”

“…geomorphological structure, sub-stratum, productivity, prey availability, riparian forest cover, and human disturbance combine to mediate species occurrence and assembly through environmental filtering of morphological and physiological traits (Manel et al. 2000; Sinha, Chatterjee, et al. 2022).”