Biodiversity is the outcome of complex processes that interact across spatial and temporal scales. In large part because of historical contingency rather than out of necessity, scientific disciplines dedicated to studying biodiversity tend to emphasize some processes over others, or tend to focus on one scale of organization while treating as inconsequential processes at higher or lower scales. The sEnigmas ECR working group arose out of a conversation between three of us with domain expertise in community ecology, population genetics, and macroevolution. We noticed that within each of our sub-disciplines there remain unexplained and even enigmatic patterns: the species-genetic diversity correlation (Vellend, 2005), Lewontin's paradox (Buffalo, 2021; Lewontin, 1974), and the diversification-genetic diversity correlation (Silva et al, in prep), respectively. Our curiosity was sparked by the feeling of apparent symmetry among these enigmas (i.e. the central importance of genetic diversity), and by the realization that they must all be facets of one grand overarching pattern which we are simply failing to ascertain with our current, limited tools.

In service of continuing this investigation we pitched our idea for "sEnigmas", which was graciously funded by sDiv as part of its first round ever of Early-Career Researcher Working Groups. The Early-Career Researcher Working Group structure had several clear benefits for our group. First, it facilitated free and equal participation of all members in plenary sessions. We discussed how conversing with a group of peers allowed people to 'speak up' without hesitating or self-censoring in a way that might be more common if an ECR were in a much larger group of senior scientists. sDiv came up with few rules for ECR groups which they hoped will help ECR colleagues successfully lead working groups. The maximum size is eight (+ two/three additional iDiv researchers if wanted and funded), so a rather small team which is easier to manage. Only two senior colleagues with no past & ongoing supervision relationships with any of the initial eight participants. This was meant to minimize potential domination of senior colleagues or potential conflicts because of power relationships.

Related to this, we found that this freedom in being among a peer group allowed us to brainstorm very effectively. This was particularly important when bringing together experts from diverse fields, because we are all only experts within our own individual domains. This free expression and a license to ask seemingly naive questions outside one's own discipline promoted bubbling activity and radical brainstorming sessions. A third benefit of this working group structure was providing space for ECR participants to take leadership roles and develop skills in facilitating group dynamics, which they otherwise might not have done in the presence of more senior researchers. When everyone is invested in participating and feels a sense of ownership for the process it generates an incredible amount of buy-in, which builds trust among group members and strengthens group cohesion.

Our approach involved bringing together theoreticians, modelers, and empirical biologists with specific expertise within the focal sub-domains, and with demonstrated interest in synthesizing across disciplinary boundaries and/or across scales of organization. The proximal goals of our working group are: 1) to develop a coherent synthesis bridging community ecology, population genetics, and macroevolution; and 2) to develop a process-based mechanistic model as a crystallization of this synthesis. The ultimate goal of our group is to understand the enigmas of biodiversity within a single unifying framework - to see each of them as facets of a greater whole, and to begin to apprehend this whole itself.

Establishing a common language linking concepts across scales and disciplines was tricky because it wasn't immediately clear that it even was a challenge until the first meeting was already underway. As an example, each member of the group from different sub-fields focused on slightly different expressions of genetic diversity, which only became clear to us some time during the second day of our first meeting. This was a wonderful teachable moment for ourselves which required us to wind back our conversation and identify the fuzzy boundaries between our lexicons.

Given that several of our group members have participated in previous 'full' working groups, it seems opportune to reflect a bit further on the benefits and challenges of the ECR versus full working group structures. One notable difference between these two structures is the group size, with ECR groups being significantly smaller. The small size of our current group (eight core members and three iDiv postdocs) promotes both focus and agility - in other words, it's easy to make decisions and to stay on task. Full working groups can be substantially larger, which can (in our experience) occasionally result in the vision and scope of projects expanding to an unmanageable level, and which can additionally result in decision-making overhead. On the other hand, the ECR exuberance and cognitive flexibility may not entirely counterbalance the (necessary) limitation in depth of early-career experience and domain knowledge. A final challenge of the ECR format, which is less critical for full working groups, is the inherent instability of ECR employment status. Several of our members have changed jobs over the course of this working group, and the majority of us have uncertain futures with respect to permanent stable positions in academia, which is a challenge in terms of maintaining continuity of participation. To be clear, sDiv has been exceedingly supportive in accommodating the needs of our group members generated by this shifting landscape of employment status.

Overall, our first two meetings were very productive, stimulating, and exciting. We are currently working on a draft manuscript to describe our cross-disciplinary synthesis, with a focus on intraspecific genetic diversity and its central role in linking processes across spatial and temporal scales. We hope to complete the draft of our theoretical synthesis in time for a potential third meeting during which we will operationalize our model within a process-based mechanistic framework, inspired by a unification of previous work of sEnigmas participants (e.g. Hagen, O. et al. 2021; Overcast, I. et al. 2021). Within the synthesis paper and the modeling framework we hope to ignite a new line of inquiry for holistically understanding biodiversity, and to reflect not only the challenges but also the vibrant discussions we have undertaken within this sDiv ECR working group.